title: Lassie (1954 TV series)

text: In 1957, both Clayton and Rettig wanted to leave the show. Producers decided to find a new boy and ease the Miller family out of the show. Two hundred boys were interviewed, and six-year-old film veteran Jon Provost was hired and made his début as Timmy in the fourth season opener, "The Runaway." In July 1957, George Cleveland died suddenly, and producers were forced to overhaul the entire show. The plot was extensively reworked, and Clayton and Rettig were completely dropped. Cloris Leachman and Jon Shepodd were quickly hired as Timmy's foster parents Ruth and Paul Martin. In the fourth season, George Chandler was hired to play Petrie Martin, Paul's uncle, but the character was later dropped. As fourth season shooting progressed, Leachman grew unhappy playing a somber farm woman, feuded on-set with co-workers and proved unpopular with viewers, which caused ratings to drop. When filming was completed for the 1957–58 season in February 1958, Wrather severed ties with producer Maxwell and dropped Leachman and Shepodd. Film veteran June Lockhart and Broadway stage star Hugh Reilly replaced Leachman and Sheppod as Ruth and Paul Martin at the top of the fifth season. Todd Ferrell played Timmy's friend Ralph "Boomer" Bates, a recurring character with his dog Mike, but both were dropped in 1959.


title: Lassie (1954 TV series)

text: Former Keystone Kop Andy Clyde, also a co-star of "The Real McCoys", became a regular in 1959 as neighbor Cully Wilson.


title: Lassie (1954 TV series)

text: Guest stars during the Timmy years included "The Lone Ranger", baseball player Roy Campanella, Olympian Rafer Johnson, Stacy Keach Sr., Marie Windsor, Dick Foran, Tod Griffin, Jane Darwell, Denver Pyle, Fuzzy Knight, Harry Carey, Jr., William Schallert, Stephen Talbot, Ellen Corby, and Karl Swenson.


title: Lassie (1954 TV series)

text: During its first four years, "Lassie" received very decent ratings. However, at the end of the 1958–1959 season, the ratings had fallen from the top 30, likely due to the constant turnover in the cast. Once viewers began to warm to Lockhart and Reilly as Timmy's parents, the Martin family was accepted and embraced by the public. As a result, between 1960 and 1964, "Lassie"s ratings greatly improved and by the spring of 1964, it received its highest rating ever, ranking at #13.


title: Lassie (1954 TV series)

text: In 1964, Provost declined to renew his contract. Producers decided to broaden the show's demographics to appeal to older viewers, and, to that end, dropped the boy and his dog theme for a plot featuring a Forest Service Ranger. Robert Bray, a former Marine and Gary Cooper look-alike was cast as Corey Stuart. During Bray's first year, the show transitioned to color filming and spectacular scenic locations across America were exploited as settings for the show. Eventually, Bray's long battle with alcoholism forced him from the show, and Jack De Mave and Jed Allan were hired to replace him.


title: Lassie (1954 TV series)

text: Guest stars during the Ranger years included Ken Osmond, Paul Petersen, Suzanne Somers, Victor French, Leo Gordon, and Morgan Brittany. When the Forest Service years came to an end, Lassie wandered the country on her own for a season then settled at the Holden ranch for her final two syndicated seasons with costars Ron Hayes, Larry Pennell, Skip Burton, Larry Wilcox, Sherry Boucher, and Pamelyn Ferdin.


title: Lassie (1954 TV series)

text: Wrather's wife, Bonita Granville Wrather, who was the series' associate producer, narrated numerous episodes throughout the run of the series, usually the beginning and/or ending of multi-part episodes.


title: Lassie (1954 TV series)

text: Many early episodes were written by Robert Maxwell under the pseudonym Claire Kennedy. In later years, the writing partnership of Robert Schaefer and Eric Freiwald was responsible for over 150 episodes. They were also responsible for developing the idea of having Lassie with a forest ranger.


title: Lassie (1954 TV series)

text: Novelist Inez Asher was among those who wrote for the series, while other scripts were produced by writers blacklisted during the heyday of McCarthyism and the House Un-American Activities Committee. These writers included Robert Lees (credited as J. E. Selby) and Adrian Scott, one of the Hollywood Ten who went to prison for contempt of the United States Congress. His wife, Joan Scott writing as "Joanne Court", attended story conferences and gave her husband notes so he could do rewrites.


title: Lassie (1954 TV series)

text: The show's first studio was Stage One of KTTV in Los Angeles, California, with the production moving to Desilu in 1957. Franklin Canyon Reservoir and Vasquez Rocks saw location shootings. During the Timmy seasons, episodes were filmed at the Grand Canyon and in the High Sierra, and, during the Forest Service seasons, the Forest Service and the Department of the Interior offered Alaska, Puerto Rico, the Washington Monument and other sites for location shoots.


title: Lassie (1954 TV series)

text: Fifteen pages were filmed per day, six days a week, with three shows completed per week. Shooting in order was not possible. Several barn segments might be filmed at a particular time with the crew then moving on to film an equal number of kitchen scenes. The shots may have then been used in four or five different episodes. Rettig was allowed to bond with the dog and often groomed the dog at the studio or spent weekends at Weatherwax's home playing with the animal. The bond translated to film, making the boy and dog scenes more believable, but, eventually the dog developed divided loyalties (looking to Rettig for direction rather than Weatherwax) and the trainer was forced to curtail the amount of time boy and dog spent together.


title: Lassie (1954 TV series)

text: Typically, there were two dog trainers on the set, each teetering on a stepladder only Lassie could see and waving a chunk of meat at the dog. "It would look as though Lassie was looking at Jon (Provost), but he was really looking past Jon at the piece of beef", Lockhart recalled in 2004. When Provost delivered his line, the trainer behind Lockhart would whisper "Lassie!" and wave another piece of meat. Lassie's head would turn to Lockhart who would deliver her line. Then the trainer behind Provost would get Lassie's attention again, and Provost would deliver his next line. "The sound editor would cut out all that," Lockhart said, "You finally got to where you never heard the trainers. Often, if the scene had gone well, and maybe we hadn't gotten the dialogue quite right, if the dog was right, they'd print it." In addition to the main Lassie, three other Lassies might be involved in an episode shoot: a stand-in for rehearsals, a stunt double, and a "fighter" for scenes involving battles with other animals.


title: Lassie (1954 TV series)

text: "Lassie" used several pieces of theme music during its long broadcast history. For the first season, "Secret of the Silent Hills (Theme from the Lassie TV series)", is used for both the opening and ending theme. Composed by William Lava, the orchestral theme was originally created for the 1940 radio show "The Courageous Dr. Christian".<ref name="Lassie /Jeffs Collie /Timmy and Lassie">Lassie /Jeffs Collie /Timmy and Lassie</ref>


title: Lassie (1954 TV series)

text: For the second and third season a variation of this theme, titled simply "Lassie Main & End Title", was used for the opening and ending theme. Raoul Kraushaar, the music director for the series, is the listed composer for the theme; however the changes he made to the original are so slight that only a trained ear can tell the difference. The third theme used for the series is an orchestral rendition of the aria, "Dio Possente" (Even Bravest Hearts May Swell) from Charles Gounod's opera, "Faust". The exact time this theme started being used is uncertain due to conflicting records; however it is agreed that it was the third series, and was used for at least part of season four for the change of ownership of Lassie.


title: Lassie (1954 TV series)

text: The most famous of the Lassie theme songs appeared at the start of the fifth season. Copyrighted as "Lassie Main & End Title", the song was created by Les Baxter, with the whistling itself performed by Muzzy Marcellino. Nicknamed "The Whistler," it remained the series theme for the rest of the "Martin years". With the coming of the "Ranger years", the opening and ending theme was changed to an orchestral version of "The Whistler". With the coming of the "Alone" years, and continuing throughout the ranch/Holden family years the theme was changed again, this time to Nathan Scott's arrangement of the traditional folk tune "Greensleeves", which become the series theme song for the rest of its run. For the final two seasons, the familiar closing visual of Lassie standing on a hill and lifting her paw, was replaced by the credits on a green background, and flashing from one slate to the other instead of scrolling as in most of the series run. Television composer Nathan Scott scored the music to nearly every episode between 1963 and 1973, except for four episodes.


title: Lassie (1954 TV series)

text: Campbell's Soup Company sponsored the entire nineteen-year run of "Lassie". In one of the first instances of product placement, the company asked that their products be visible on the set and so, in episode after episode, Campbell's products are seen in background shots. Campbell's also contractually required the show's stars to avoid appearing in any film or theatrical production that undermined their All-American images.


title: Lassie (1954 TV series)

text: In 1956, the company held a "Name Lassie's Puppies" contest with the grand prizes being Lassie's pups and $2,000. Company executives hand-delivered puppies to the winner's homes. In 1958, for twenty-five cents and a label from a Swanson's frozen dinner, viewers could receive a Lassie portrait friendship ring based on one that Uncle Petrie fashions for Timmy. The company mailed 77,715 rings to viewers. In 1959, the company offered a wallet "made of rich brown plastic" emblazoned with a picture of Lassie; 1,343,509 wallets were mailed to viewers who sent in five different labels from Campbell products. The labels represented 6.5 million cans of Campbell's products sold. Campbell's paid the Wrather Company $7 million a year to air its commercials. The soup company's profits rose seventy percent over its pre-"Lassie" days.


title: Lassie (1954 TV series)

text: Lassie was spokesdog for Recipe Dog Food, a Campbell's product introduced in 1969, which was reportedly based on the homemade stew mixture Weatherwax prepared for Lassie. Printed advertisements for the product announced, "Now all dogs can come home to the dinner Lassie comes home to." In its first year, Recipe earned $10 million for Campbell's, and, in its third year, $40 million. To help boost sales, Campbell's paid Weatherwax to write a dog-training manual called "The Lassie Method" which the company used as a premium offer.


title: Lassie (1954 TV series)

text: Plots during the first 10 "boy and his dog" seasons were similar: the boy (Jeff or Timmy) got into some sort of trouble. Lassie then dashed off to get help or rushed in to save her master's life herself. After being reunited with family and breathing a sigh of relief, the boy received a light lecture on why he should not have done what he had done. In 2004, June Lockhart described the show as "a fairy tale about people on a farm in which the dog solves all the problems in 22 minutes, in time for the last commercial."


title: Lassie (1954 TV series)

text: Two "Timmy and Lassie" episodes launched Campbell's Soup premiums, while two others promoted a UNICEF Halloween project and the Peace Patrol, a children's savings bond program spearheaded by "Lassie" and "The Lone Ranger". The same seasons saw several Christmas episodes, while conservation and environmentalism were brought center stage. Some scripts dealt with race and ethnicity with both Jeff and Timmy championing Hispanics, Native Americans, and Asian Americans. Aging Americans were presented in a positive light during the years when Andy Clyde was featured as Martin family friend/neighbor Cully Wilson.


title: Lassie (1954 TV series)

text: Seasons 11–16 were the "Ranger years" of the series, as Lassie (because she was not able to go to Australia with the Martins when Paul got a job teaching agriculture there) was taken in by U.S. Forest Ranger Corey Stuart (who appeared in a few episodes of season 10) and began to work with the U.S. Forest Service. Color filming was exploited during the Ranger years with Lassie and her friends sent to exotic locations such as Sequoia National Forest and Monument Valley, creating miniature travelogues for viewers. Other rangers would be featured during the latter part of this era when Robert Bray (who played Stuart) left the series.


title: Lassie (1954 TV series)

text: For season 17, the program shifted gears again and became somewhat of an anthology series, with Lassie traveling on her own, getting into different adventures each week (similar in format to "The Littlest Hobo"). No explanation was given as to why Lassie was no longer with the Forest Service. Some episodes during this final CBS season were animals-only.


title: Lassie (1954 TV series)

text: During seasons 18 and 19 (with the series having moved to first run syndication), Lassie was taken in by Garth Holden (played by Ron Hayes) who was in charge of the Holden Ranch – a home for orphaned boys – which he ran with his college-age son and his friend. This (somewhat) brought the show back to its roots by giving Lassie a farm/ranch home base, which is where she settled in for the final two years of the series.


title: Lassie (1954 TV series)

text: "Lassie" themes explored the relationship between boys and their dogs with the show helping to shape the viewer's understanding of mid-twentieth century American boyhood. "Lassie" was associated with the wholesome family values of its period but some parents' groups monitoring television content found cliffhanger plots showing children in danger too intense for very young viewers and objected to some of Timmy's actions which were believed to encourage children to disobey parents. However, Lassie was consistently depicted as caring, nurturing, and responsible with a commitment to family and community, often rescuing those in peril and righting wrongs. She was the perfect 'mother' within the American ideology of the 1950s and 1960s.


title: Lassie (1954 TV series)

text: First-run "Lassie" was televised September 12, 1954 to March 24, 1973 with its first 17 seasons airing on CBS Sundays at 7:00 p.m. EST. In 1971, in order to promote community-related programming among local affiliates, the Federal Communications Commission moved primetime Sundays to 8:00 P.M. EST with the institution of the Prime Time Access Rule. CBS executives felt "Lassie" would not be well received in a time slot other than its traditional 7:00 p.m. slot, and, with the network's other family programs set, the show was canceled. ("Lassie" was among several shows that CBS canceled during this time period as part of a change in its target demographics.) "Lassie" then entered first-run syndication with Jack Wrather and Campbell's Soup still on board, and remained on the air for another two years with its final episode airing in March 1973. All totaled, 591 episodes were produced.


title: Lassie (1954 TV series)

text: An animated reworking, "Lassie's Rescue Rangers", followed in fall 1973, immediately after the original series ended (the pilot movie aired in 1972 while the live-action series was still on the air). "Lassie's Rescue Rangers" was denounced by both Weatherwax and the National Association of Broadcasters, the latter of which made note of the animated series' "violence, crime and stupidity."


title: Lassie (1954 TV series)

text: The Miller years were sold into syndication in 1958 under the title of "Jeff's Collie". In rerun syndication, the Martin family episodes aired under the title of "Timmy & Lassie." Re-runs of the series aired on Nickelodeon from 1984 until 1996.


title: Lassie (1954 TV series)

text: While the original series had no direct spinoffs, a few subsequent productions would use the Lassie character.


title: Lassie (1954 TV series)

text: In 1973, ABC created an animated Saturday-morning animated program called "Lassie's Rescue Rangers" produced by Filmation.


title: Lassie (1954 TV series)

text: In 1989, what was essentially a sequel series, "The New Lassie" – featuring Jon Provost as Steve McCullough – aired in first-run syndication. In its seventh episode ("Roots"), June Lockhart reprised her Ruth Martin role when Steve McCullough is revealed to be the adult Timmy Martin. It is revealed that Timmy was never properly adopted by the Martins and consequently was forced to remain in the U.S. when Ruth and Paul emigrated to Australia. Timmy was then subsequently adopted by the McCullough family and began going by his middle name Steven. In 1992, Tommy Rettig made a guest appearance in the final episode, "The Computer Study". This would be his last television appearance prior to his death in 1996.


title: Lassie (1954 TV series)

text: In 1997, a modified remake – also called "Lassie" – debuted, airing in the U.S. on the then new Animal Planet cable network. This show (which was filmed in Canada and set in Vermont) also revolved around a boy named Timmy and his dog, though differences in setting and character circumstances precluded it from being an exact remake of the original series.


title: Lassie (1954 TV series)

text: During Thanksgiving week 1962, a five-part color episode called "The Journey". was filmed in the High Sierra. First telecast in February and March 1963, the episode follows Timmy and Lassie, as the two are swept away in a carnival hot air balloon that eventually comes to rest in the Canadian wilderness. The voyagers face many perils before being rescued by the Royal Canadian Mounted Police. Richard Simmons, star of another Jack Wrather property, "Sergeant Preston of the Yukon", made an appearance, while "Lassie" star Jon Provost performed whitewater stunts. "Lassie" sponsor Campbell's Soup objected to multi-part episodes, believing viewers would not want to tune in week after week to find out what happened from one segment to the next, but three of the five segments of "The Journey" hit the Nielsen top ten for the weeks in which they aired. The five segments were later edited into a feature-length film and released in August 1963 through 20th Century Fox as "Lassie's Great Adventure".


title: Lassie (1954 TV series)

text: Every year of its 17-year run on CBS, "Lassie" placed first in its time slot, Sunday 7:00 P.M. EST, and often ranked among the top 25 shows on television. The show's highest ranking years in the Nielsen ratings were the Martin years when the show placed #24 in 1957, #22 in 1958, #15 in 1959, #15 in 1961, #21 in 1962, #13 in 1963, and #17 in 1964. The only Martin year "Lassie" did not climb into the top twenty-five was 1960, when it ran opposite "Walt Disney Presents" on ABC and "Shirley Temple Theater" on NBC. However, "Lassie" still ran opposite Disney when the Disney anthology television series moved to NBC in 1961, and still managed to climb into the Top 25. With the advent of the Forest Service seasons, the show began a steady decline in ratings.


title: Lassie (1954 TV series)

text: In 1960, the Lassie character became one of only three live canine characters to receive a star on the Hollywood Walk of Fame.


title: Lassie (1954 TV series)

text: Ancillary merchandise produced during the show's first-run includes Halloween costumes, Viewmaster reels, comic books, and other items. In 2005, Karen Pfeiffer released "The Legacy of Lassie: An Unauthorized Information and Price Guide on Lassie Collectibles" ().


title: Lassie (1954 TV series)

text: In 1967, in conjunction with Lassie's association with the United States Forest Service and environmentalism, Lassie was welcomed to the White House by Lady Bird Johnson. In January 1968, President Lyndon Johnson signed into a law a bill targeting soil and water pollution that many called "the Lassie program". Lassie and her sponsors were honored with a luncheon in the Senate Dining Room on March 19, 1968, and presented with a plaque by senators Edmund Muskie and George Murphy, recognizing their commitment to the environment.


title: Lassie (1954 TV series)

text: Jon Provost called his autobiography "Timmy's in the Well!" because a well was the one place Timmy never fell into—abandoned mine shafts, off cliffs, into rivers, lakes, and quicksand, but never a well.


title: Lassie (1954 TV series)

text: "Mad" parodied the show as "Lizzy", where it was revealed that the collie was actually a circus midget in a dog suit, while the real Lizzy was a dimwitted mutt.


title: Lassie (1954 TV series)

text: In an episode of "The Flintstones" ("Dino Goes Hollyrock"), the character Dino wins an appearance on the smash hit TV show "Sassie" starring a heavily made-up and snobby girl dinosaur and her Lassie-like adventures.


title: Lassie (1954 TV series)

text: Belgian comics artist Willy Vandersteen created his own version of the TV show with a collie named "Bessy" in 1954. Apart from the fact that his comic strip starred the same dog breed with a similar name, it had little to do with the series overall, since the comic was a Western comic.


title: Eritrean War of Independence

text: The Eritrean War of Independence was a war for independence which Eritrean independence fighters waged against successive Ethiopian governments from 1 September 1961 to 24 May 1991.


title: Eritrean War of Independence

text: Eritrea was an Italian colony from the 1880s until the defeat of the Italians by the Allies of World War II in 1941, Eritrea then briefly became a British protectorate until 1951. The General Assembly of the United Nations held a meeting about the fate of Eritrea, in which the majority of the delegates voted for the federation of Eritrea with Ethiopia, and Eritrea became a constituent state of the Federation of Ethiopia and Eritrea in 1952. The Federation was supposed to last for ten years in which Eritreans could have mini sovereign decisions such as a parliament and some autonomy, but under the Ethiopian crown for further ones. The Assembly also assigned commissioner Anzio Mattienzo to supervise the process. Eritreans were supposed to claim Eritrea as an independent sovereign state after the ten years of federation. However, Eritrea's declining autonomy and growing discontent with Ethiopian rule caused an independence movement led by the Eritrean Liberation Front (ELF) in 1961. Hamid Idris Awate officially began the Eritrean armed struggle for independence on 1 September 1961 on the mountain of Adal, near the town of Agordat in south western Eritrea. Ethiopia annexed Eritrea the next year.


title: Eritrean War of Independence

text: Following the Ethiopian Revolution in 1974, the Derg abolished the Ethiopian Empire and established a Marxist-Leninist communist state. The Derg enjoyed support from the Soviet Union and other communist nations in fighting against the Eritreans. The ELF was supported diplomatically and militarily by various countries, particularly the People's Republic of China, which supplied the ELF with weapons and training until 1972, when Ethiopia recognized Beijing as the legitimate government of China.


title: Eritrean War of Independence

text: The Eritrean People's Liberation Front (EPLF) became the main liberation group in 1977, expelling the ELF from Eritrea, then exploiting the Ogaden War to launch a war of attrition against Ethiopia. The Ethiopian government under the Workers Party of Ethiopia lost Soviet support at the end of the 1980s and were overwhelmed by Ethiopian anti-government groups, allowing the EPLF to defeat Ethiopian forces in Eritrea in May 1991.


title: Eritrean War of Independence

text: The Ethiopian People's Revolutionary Democratic Front (EPRDF), with the help of the EPLF, defeated the People's Democratic Republic of Ethiopia (PDRE) when it took control of the capital Addis Ababa a month later. In April 1993, the Eritrean people voted almost unanimously in favour of independence in the Eritrean independence referendum, with formal international recognition of an independent, sovereign Eritrea in the same year.


title: Eritrean War of Independence

text: The Italians colonised Eritrea in 1882 and ruled it until 1941. In 1936, Italy invaded Ethiopia and declared it part of their colonial empire, which they called Italian East Africa. Italian Somaliland and Eritrea were also part of that entity, ruled by a Governor-General or Viceroy.


title: Eritrean War of Independence

text: Conquered by the Allies in 1941, Italian East Africa was sub-divided. Ethiopia liberated its formerly Italian occupied land in 1941. Italian Somaliland remained under Italian rule, but as a United Nations protectorate not a colony, until 1960 when it united with British Somaliland, to form the independent state of Somalia.


title: Eritrean War of Independence

text: Eritrea was made a British protectorate from the end of World War II until 1951. However, there was debate as to what should happen with Eritrea after the British left. The British delegation to the United Nations proposed that Eritrea be divided along religious lines with the Christians to Ethiopia and the Muslims to Sudan. In 1952, the United Nations decided to federate Eritrea to Ethiopia, hoping to reconcile Ethiopian claims of sovereignty and Eritrean aspirations for independence. About nine years later, Ethiopian Emperor Haile Selassie dissolved the federation and annexed Eritrea, triggering a thirty-year armed struggle in Eritrea.


title: Eritrean War of Independence

text: During the 1960s, the Eritrean independence struggle was led by the Eritrean Liberation Front (ELF). The independence struggle can properly be understood as the resistance to the annexation of Eritrea by Ethiopia long after the Italians left the territory. Additionally, one may consider the actions of the Ethiopian Monarchy against Muslims in the Eritrean government as a contributing factor to the revolution. At first, this group factionalized the liberation movement along ethnic and geographic lines. The initial four zonal commands of the ELF were all lowland areas and primarily Muslim. Few Christians joined the organization in the beginning, fearing Muslim domination.


title: Eritrean War of Independence

text: After growing disenfranchisement with Ethiopian occupation, highland Christians began joining the ELF. This growing influx of Christian volunteers prompted the opening of the fifth (highland Christian) command. Internal struggles within the ELF command coupled with sectarian violence among the various zonal groups splintered the organization.


title: Eritrean War of Independence

text: The war started on 1 September 1961 with the Battle of Adal, when Hamid Idris Awate and his companions engaged the occupying Ethiopian Army and police. In 1962, Emperor Haile Selassie unilaterally dissolved the federation and the Eritrean parliament and annexed the country.


title: Eritrean War of Independence

text: The Eritrean Liberation Front (ELF), was founded in 1961 by a handful of exiled Eritreans, began guerrilla operations against the Imperial Government in the fashion of the traditional bandits of that province. By 1966, it had a free hand in much of the barren lowlands in western and coastal Eritrea. The movement enjoyed military aid from various Arab countries as virtually all of its leaders were Muslims. However, the leadership of the ELF was often inept; and communications between roving guerrilla bands and the exiled leaders were sporadic at best. Nonetheless, it was able to infiltrate small arms and returning trainees by way of Sudan and the Red Sea coast, and harass Imperial forces in Eritrea. The ELF was mostly made up of Muslim tribes such as the Tigre, Saho and Nara.


title: Eritrean War of Independence

text: The Imperial Ethiopian Army, whose Second Division was based in Eritrea, made periodic sweeps through the countryside. The Israeli trained commando police were more efficient than the army. But the commando police was too few in number to protect important installations and also pursue the insurgents. And the Second Division was heavily resented by the Eritrean populace and was not very effective. Its normal tactics were to burn down villages, arrest suspects, and destroy livestock—the traditional Ethiopian responses to dissidence.


title: Eritrean War of Independence

text: In 1970 members of the ELF had a falling out, and several different groups broke away from the group. During this time, the ELF and the groups that later joined to form the Eritrean People's Liberation Front (EPLF) fought a bitter civil war. The two organizations were forced by popular will to reconcile in 1975 and participated in joint operations against Ethiopia.


title: Eritrean War of Independence

text: In 1974, Emperor Haile Selassie was ousted in a coup. The new Ethiopian government, called the Derg, was a Marxist military junta, which eventually came to be controlled by strongman Mengistu Haile Mariam. The new Derg regime took an additional three to four years to get complete control of both Ethiopia, Eritrea, and parts of Somalia. After this change of government, followed by international recognition, Ethiopia began a strategic alliance with the Soviet Union.


title: Eritrean War of Independence

text: Many of the groups that splintered from the ELF joined in 1977 and formed the EPLF. By the late 1970s, the EPLF had become the dominant armed Eritrean group fighting against the Ethiopian government. The leader of the umbrella organization was Secretary-General of the EPLF Ramadan Mohammed Nour, while the Assistant Secretary-General was Isaias Afewerki.


title: Eritrean War of Independence

text: During this time, the Derg could not control the population by force alone. To supplement its garrisons, forces were sent on missions to instill fear in the population, including massacres which took place in primarily Muslim parts of Eritrea, including the villages of She'eb, Hirgigo, Elabared, and the town of Om Hajer; massacres also took place in predominately Christian areas as well. The advent of these brutal killings of civilians regardless of race, religion, or class was the final straw for many Eritreans who were not involved in the war, and at this point many either fled the country or went to the front lines.


title: Eritrean War of Independence

text: From 1975 to 1977, the ELF and EPLF outnumbered the Ethiopian army and liberated all of Eritrea except Asmara, Massawa, and Barentu. By 1977, the EPLF was poised to drive the Ethiopians out of Eritrea, by utilizing a simultaneous military invasion from the east by Somalia in the Ogaden to siphon off Ethiopian military resources. But in a dramatic turnaround, the Derg managed to repulse the Somali incursion, thanks mainly to a massive airlift of Soviet arms. After that, using the considerable manpower and military hardware available from the Somali campaign, the Ethiopian Army regained the initiative and forced the EPLF to retreat. This was most notable in the Battle of Barentu and the Battle of Massawa.


title: Eritrean War of Independence

text: In May 1978, using a newly completed airfield in Mekelle in neighboring Tigray, the Ethiopian air force began a campaign of saturation bombing of positions in Eritrea held by the ELF and EPLF. While many of the targets hit were military, the bombers also attacked towns, villages and animal herds. The ground offensive started in July, and in a few weeks captured all the towns that the ELF and EPLF had held in southern and central Eritrea. The second offensive began in November 1978, aimed at the relief of Massawa and the recapture of Keren. An even larger army was deployed, including large contingents of armor. On November 25–26, there was a huge two-day battle with the EPLF at Elabored, which ended inconclusively. However, the EPLF was badly mauled and decided to abandon Keren and the nearby towns, and withdraw to the mountains of Sahel, where the terrain was appropriate for a last stand. This was called the "strategic withdrawal." The ELF, which had taken the brunt of the first offensive, refused to pull out of the newly liberated areas. By continuing to engage the Ethiopian army, rather than retreat, the ELF ensured its military defeat.


title: Eritrean War of Independence

text: The third offensive took place in January–February 1979, and consisted in a three- pronged attack on Nakfa, the headquarters of Sahel district, where the EPLF had set up its "liberated area" and was beginning to construct defensive lines. More areas were evacuated in the face of the assault, and the EPLF was able to dismantle and remove the infrastructure more systematically.


title: Eritrean War of Independence

text: The fourth offensive was launched towards Nafka in March 1979, the fifth offensive was then launched in July. The army Chief of Staff wrote a newspaper article anticipating total victory, entitled: "Days of remnants of secessionist bandits lurking in bushes numbered." Over 50,000 troops were deployed in the attacks, together with large amounts of armor. Most of the attacks were destroyed well short of their target. Between July 14 and 22, the army lost an estimated 6,000


title: Eritrean War of Independence

text: Another offensive, launched towards Nakfa in December 1979, ended in a disaster and rout for government forces. The EPLF was able to counter-attack and push the army back as far as its headquarters at Afabet.


title: Eritrean War of Independence

text: In December 1980 the government launched a relatively small attack, which petered out without military gains to either side. 1981 passed without a major military offensive.


title: Eritrean War of Independence

text: The alliance between the EPLF and the ELF which had held since 1975 began to break, and quickly developed into an irrevocable split. There were some armed clashes between the groups, for instance in August 1980, but large-scale civil war was avoided in part because of military weakness of the ELF. The Tigray People's Liberation Front (TPLF) assisted the EPLF in its attacks on ELF positions. Most of the ELF fighters retreated into Sudan, where they were detained and disarmed by the Sudanese government. The last major group arrived in Karakon, eastern Sudan, in 1981.


title: Eritrean War of Independence

text: After the comparative lull of 1980–1, 1982 was to be the worst year of war in Eritrea to date, in which the government made an all-out attempt to crush the EPLF. It was named the Red Star Campaign in response to the planned US "Bright Star" exercises in the Middle East. Mengistu Haile Mariam then went to Asmara to personally oversee the offensive himself. The Red Star Campaign involved the largest number of troops ever deployed in Eritrea—more than 120,000 were involved in the attacks on the EPLF base areas. The forcefully conscripted soldiers in the Ethiopian ranks were used for massive assaults on the EPLF positions around Nakfa, in the hope that sheer weight of numbers would overrun the rebel lines. The offensive involved an unprecedented use of air power and toxic gas. The EPLF had to equip it's fighters with homemade gas masks. Despite inflicting devastating casualties on the EPLF, the Ethiopians failed to breakthrough the rebel lines. The Red Star offensive failed. By May 1982, it had failed to capture Nafka, and it was unofficially abandoned on June 20. The EPLF was even able to counter-attack and push government lines back. Having been launched with huge publicity, the offensive ended in complete silence from the government media.


title: Eritrean War of Independence

text: In 1983, the government launched an offensive in March on the Halhal front, north of Keren. Known as the "Stealth Offensive" because of the lack of publicity surrounding it, government forces succeeded in overrunning EPLF lines, but not in inflicting a significant defeat on the rebels.


title: Eritrean War of Independence

text: In early 1984, the EPLF went on the offensive, making some significant gains. The government responded by another round of aerial bombardment, and by an offensive launched on 27 October which inflicted heavy casualties on the Eritreans and forced them to retreat back to their original lines.


title: Eritrean War of Independence

text: In the summer of 1985, the EPLF again went on the offensive and expelled the Ethiopians from the town of Barentu. The Derg then sent freshly conscripted recruits and threw them at the entrenched Eritreans to force them out of Barentu, the result was a costly victory for the Ethiopians as they were able to push out the Eritreans but not after talking significant casualties.


title: Eritrean War of Independence

text: In 1986 the Derg launched the “Red Sea Offensive” and attacked the frontlines of the EPLF with the aim of capturing Nafka, despite extensive air support and the use of airborne troops in the Sahel the Ethiopians were repelled. As insurgencies in Tigray, Wollo and other parts of Ethiopia began to grow worse the government no longer had the resources to conduct massive offensives in Eritrea and had to focus on other regions as well.


title: Eritrean War of Independence

text: In 1988, with the Battle of Afabet, the EPLF captured Afabet and its surroundings, then headquarters of the Ethiopian Army in northeastern Eritrea, prompting the Ethiopian Army to withdraw from its garrisons in Tessenei, Barentu and Agordat leaving all of western and northern Eritrea into EPLF hands. EPLF fighters then moved into position around Keren, Eritrea's second-largest city.


title: Eritrean War of Independence

text: The Soviet Union informed Mengistu that it would not be renewing its defence and cooperation agreement. With the cessation of Soviet support and supplies, the Ethiopian Army's morale plummeted, and the EPLF, along with other Ethiopian rebel forces, began to advance on Ethiopian positions.


title: Eritrean War of Independence

text: In February 1990, the EPLF launched Operation Fenkil to capture the city of Massawa. The Ethiopian garrison initially put up fierce resistance until the EPLF used naval units to flak the Ethiopians. The Eritreans were able to overcome the Ethiopian defences and capture the city. After Massawa was captured by the EPLF the government launched a devastating air raid on the city with the use of cluster bombs killing hundreds of civilians.


title: Eritrean War of Independence

text: In 1991, the Ethiopian People's Revolutionary Democratic Front (EPRDF) had begun advancing towards the capital forcing Mengistu Haile Mariam to flee the country. By May 1991, the rebels had captured Addis Ababa and overthrew the government. Around the same time, the Ethiopian garrison in Asmara withdrew allowing the EPLF fighters to enter the city. The last battle took place on May 25 in Assab, when the EPLF defeated the last remnants of government loyalists.


title: Eritrean War of Independence

text: The former President of the United States, Jimmy Carter, with the help of some U.S. government officials and United Nations officials, attempted to mediate in peace talks with the EPLF, hosted by the Carter Presidential Center in Atlanta, Georgia in September 1989. Ashagre Yigletu, Deputy Prime Minister of the People's Democratic Republic of Ethiopia (PDRE), helped negotiate and signed a November 1989 peace deal with the EPLF in Nairobi, along with Jimmy Carter and Al-Amin Mohamed Seid. However, soon after the deal was signed, hostilities resumed. Yigletu also led the Ethiopian government delegations in peace talks with the TPLF leader Meles Zenawi in November 1989 and March 1990 in Rome. He also attempted again to lead the Ethiopian delegation in peace talks with the EPLF in Washington, D.C. until March 1991.


title: Eritrean War of Independence

text: After the end of the Cold War, the United States played a facilitative role in the peace talks in Washington, D.C. during the months leading up to the May 1991 fall of the Mengistu regime. In mid-May, Mengistu resigned as head of the Ethiopian government and went into exile in Zimbabwe, leaving a caretaker government in Addis Ababa. A high-level U.S. delegation was present in Addis Ababa for the 1–5 July 1991 conference that established a transitional government in Ethiopia. Having defeated the Ethiopian forces in Eritrea, the EPLF attended as an observer and held talks with the new transitional government regarding Eritrea's relationship to Ethiopia. The outcome of those talks was an agreement in which the Ethiopians recognized the right of the Eritreans to hold a referendum on independence. The referendum was held in April 1993 and the Eritrean people voted almost unanimously in favour of independence, with the integrity of the referendum being verified by the UN Observer Mission to Verify the Referendum in Eritrea (UNOVER). On 28 May 1993, the United Nations formally admitted Eritrea to its membership. Below are the results from the referendum:


title: Euler equations (fluid dynamics)

text: In fluid dynamics, the Euler equations are a set of quasilinear partial differential equations governing adiabatic and inviscid flow. They are named after Leonhard Euler. In particular, they correspond to the Navier–Stokes equations with zero viscosity and zero thermal conductivity.


title: Euler equations (fluid dynamics)

text: The Euler equations can be applied to incompressible or compressible flow. The incompressible Euler equations consist of Cauchy equations for conservation of mass and balance of momentum, together with the incompressibility condition that the flow velocity is a solenoidal field. The compressible Euler equations consist of equations for conservation of mass, balance of momentum, and balance of energy, together with a suitable constitutive equation for the specific energy density of the fluid. Historically, only the equations of conservation of mass and balance of momentum were derived by Euler. However, fluid dynamics literature often refers to the full set of the compressible Euler equations – including the energy equation – as "the compressible Euler equations".


title: Euler equations (fluid dynamics)

text: The mathematical characters of the incompressible and compressible Euler equations are rather different. For constant fluid density, the incompressible equations can be written as a quasilinear advection equation for the fluid velocity together with an elliptic Poisson's equation for the pressure. On the other hand, the compressible Euler equations form a quasilinear hyperbolic system of conservation equations.


title: Euler equations (fluid dynamics)

text: The Euler equations can be formulated in a "convective form" (also called the "Lagrangian form") or a "conservation form" (also called the "Eulerian form"). The convective form emphasizes changes to the state in a frame of reference moving with the fluid. The conservation form emphasizes the mathematical interpretation of the equations as conservation equations for a control volume fixed in space (which is useful


title: Euler equations (fluid dynamics)

text: The Euler equations first appeared in published form in Euler's article "Principes généraux du mouvement des fluides", published in "Mémoires de l'Académie des Sciences de Berlin" in 1757 (although Euler had previously presented his work to the Berlin Academy in 1752).


title: Euler equations (fluid dynamics)

text: The Euler equations were among the first partial differential equations to be written down, after the wave equation. In Euler's original work, the system of equations consisted of the momentum and continuity equations, and thus was underdetermined except in the case of an incompressible flow. An additional equation, which was called the adiabatic condition, was supplied by Pierre-Simon Laplace in 1816.


title: Euler equations (fluid dynamics)

text: During the second half of the 19th century, it was found that the equation related to the balance of energy must at all times be kept for compressible flows, and the adiabatic condition is a consequence of the fundamental laws in the case of smooth solutions. With the discovery of the special theory of relativity, the concepts of energy density, momentum density, and stress were unified into the concept of the stress–energy tensor, and energy and momentum were likewise unified into a single concept, the energy–momentum vector.


title: Euler equations (fluid dynamics)

text: In convective form (i.e., the form with the convective operator made explicit in the momentum equation), the incompressible Euler equations in case of density constant in time and uniform in space are:


title: Euler equations (fluid dynamics)

text: The first equation is the Euler momentum equation with uniform density (for this equation it could also not be constant in time). By expanding the material derivative, the equations become:


title: Euler equations (fluid dynamics)

text: where formula_12 is the mechanic pressure. The second equation is the incompressible constraint, stating the flow velocity is a solenoidal field (the order of the equations is not causal, but underlines the fact that the incompressible constraint is not a degenerate form of the continuity equation, but rather of the energy equation, as it will become clear in the following). Notably, the continuity equation would be required also in this incompressible case as an additional third equation in case of density varying in time "or" varying in space. For example, with density uniform but varying in time, the continuity equation to be added to the above set would correspond to:


title: Euler equations (fluid dynamics)

text: So the case of constant and uniform density is the only one not requiring the continuity equation as additional equation regardless of the presence or absence of the incompressible constraint. In fact, the case of incompressible Euler equations with constant and uniform density discussed here is a toy model featuring only two simplified equations, so it is ideal for didactical purposes even if with limited physical relevancy.


title: Euler equations (fluid dynamics)

text: The equations above thus represent respectively conservation of mass (1 scalar equation) and momentum (1 vector equation containing formula_14 scalar components, where formula_14 is the physical dimension of the space of interest). Flow velocity and pressure are the so-called "physical variables".


title: Euler equations (fluid dynamics)

text: In a coordinate system given by formula_16 the velocity and external force vectors formula_1 and formula_18 have components formula_19 and formula_20, respectively. Then the equations may be expressed in subscript notation as:


title: Euler equations (fluid dynamics)

text: where the formula_22 and formula_23 subscripts label the "N"-dimensional space components, and formula_24 is the Kroenecker delta. The use of Einstein notation (where the sum is implied by repeated indices instead of sigma notation) is also frequent.


title: Euler equations (fluid dynamics)

text: Although Euler first presented these equations in 1755, many fundamental questions about them remain unanswered.


title: Euler equations (fluid dynamics)

text: In three space dimensions, in certain simplified scenarios, the Euler equations produce singularities.


title: Euler equations (fluid dynamics)

text: Smooth solutions of the free (in the sense of without source term: g=0) equations satisfy the conservation of specific kinetic energy:


title: Euler equations (fluid dynamics)

text: In the one dimensional case without the source term (both pressure gradient and external force), the momentum equation becomes the inviscid Burgers equation:


title: Euler equations (fluid dynamics)

text: In order to make the equations dimensionless, a characteristic length formula_27, and a characteristic velocity formula_28, need to be defined. These should be chosen such that the dimensionless variables are all of order one. The following dimensionless variables are thus obtained:


title: Euler equations (fluid dynamics)

text: Substitution of these inversed relations in Euler equations, defining the Froude number, yields (omitting the * at apix):


title: Euler equations (fluid dynamics)

text: Euler equations in the Froude limit (no external field) are named free equations and are conservative. The limit of high Froude numbers (low external field) is thus notable and can be studied with perturbation theory.


title: Euler equations (fluid dynamics)

text: The conservation form emphasizes the mathematical properties of Euler equations, and especially the contracted form is often the most convenient one for computational fluid dynamics simulations. Computationally, there are some advantages in using the conserved variables. This gives rise to a large class of numerical methods


title: Euler equations (fluid dynamics)

text: The free Euler equations are conservative, in the sense they are equivalent to a conservation equation:


title: Euler equations (fluid dynamics)

text: where the conservation quantity formula_33 in this case is a vector, and formula_34 is a flux matrix. This can be simply proved.


title: Euler equations (fluid dynamics)

text: For certain problems, especially when used to analyze compressible flow in a duct or in case the flow is cylindrically or spherically symmetric, the one-dimensional Euler equations are a useful first approximation. Generally, the Euler equations are solved by Riemann's method of characteristics. This involves finding curves in plane of independent variables (i.e., formula_35 and formula_36) along which partial differential equations (PDEs) degenerate into ordinary differential equations (ODEs). Numerical solutions of the Euler equations rely heavily on the method of characteristics.


title: Euler equations (fluid dynamics)

text: The first equation, which is the new one, is the incompressible continuity equation. In fact the general continuity equation would be:


title: Euler equations (fluid dynamics)

text: The incompressible Euler equations in the Froude limit are equivalent to a single conservation equation with conserved quantity and associated flux respectively:


title: Euler equations (fluid dynamics)

text: Here formula_33 has length formula_43 and formula_34 has size formula_45. In general (not only in the Froude limit) Euler equations are expressible as:


title: Euler equations (fluid dynamics)

text: In differential convective form, the compressible (and most general) Euler equations can be written shortly with the material derivative notation:


title: Euler equations (fluid dynamics)

text: The equations above thus represent conservation of mass, momentum, and energy: the energy equation expressed in the variable internal energy allows to understand the link with the incompressible case, but it is not in the simplest form.


title: Euler equations (fluid dynamics)

text: Mass density, flow velocity and pressure are the so-called "convective variables" (or physical variables, or lagrangian variables), while mass density, momentum density and total energy density are the so-called "conserved variables" (also called eulerian, or mathematical variables).


title: Euler equations (fluid dynamics)

text: Coming back to the incompressible case, it now becomes apparent that the "incompressible constraint" typical of the former cases actually is a particular form valid for incompressible flows of the "energy equation", and not of the mass equation. In particular, the incompressible constraint corresponds to the following very simple energy equation:


title: Euler equations (fluid dynamics)

text: Thus for an incompressible inviscid fluid the specific internal energy is constant along the flow lines, also in a time-dependent flow. The pressure in an incompressible flow acts like a Lagrange multiplier, being the multiplier of the incompressible constraint in the energy equation, and consequently in incompressible flows it has no thermodynamic meaning. In fact, thermodynamics is typical of compressible flows and degenerates in incompressible flows.


title: Euler equations (fluid dynamics)

text: meaning that for an incompressible inviscid nonconductive flow a continuity equation holds for the internal energy.


title: Euler equations (fluid dynamics)

text: And by substituting the latter in the energy equation, one obtains that the enthalpy expression for the Euler energy equation:


title: Euler equations (fluid dynamics)

text: In a reference frame moving with an inviscid and nonconductive flow, the variation of enthalpy directly corresponds to a variation of pressure.


title: Euler equations (fluid dynamics)

text: In thermodynamics the independent variables are the specific volume, and the specific entropy, while the specific energy is a function of state of these two variables.


title: Euler equations (fluid dynamics)

text: This equation is the only belonging to general continuum equations, so only this equation have the same form for example also in Navier-Stokes equations.


title: Euler equations (fluid dynamics)

text: On the other hand, the pressure in thermodynamics is the opposite of the partial derivative of the specific internal energy with respect to the specific volume:


title: Euler equations (fluid dynamics)

text: since the internal energy in thermodynamics is a function of the two variables aforementioned, the pressure gradient contained into the momentum equation should be explicited as:


title: Euler equations (fluid dynamics)

text: can be furtherly simplified in convective form by changing variable from specific energy to the specific entropy: in fact the first law of thermodynamics in local form can be written:


title: Euler equations (fluid dynamics)

text: now the term between parenthesis is identically zero according to the conservation of mass, then the Euler energy equation becomes simply:


title: Euler equations (fluid dynamics)

text: In the general case and not only in the incompressible case, the energy equation means that for an inviscid thermodynamic fluid the specific entropy is constant along the flow lines, also in a time-dependent flow. Basing on the mass conservation equation, one can put this equation in the conservation form:


title: Euler equations (fluid dynamics)

text: On the other hand, the two second-order partial derivatives of the specific internal energy in the momentum equation require the specification of the fundamental equation of state of the material considered, i.e. of the specific internal energy as function of the two variables specific volume and specific entropy:


title: Euler equations (fluid dynamics)

text: The "fundamental" equation of state contains all the thermodynamic information about the system (Callen, 1985), exactly like the couple of a "thermal" equation of state together with a "caloric" equation of state.


title: Euler equations (fluid dynamics)

text: The Euler equations in the Froude limit are equivalent to a single conservation equation with conserved quantity and associated flux respectively:


title: Euler equations (fluid dynamics)

text: Here formula_33 has length N + 2 and formula_34 has size N(N + 2). In general (not only in the Froude limit) Euler equations are expressible as:


title: Euler equations (fluid dynamics)

text: We remark that also the Euler equation even when conservative (no external field, Froude limit) have no Riemann invariants in general. Some further assumptions are required


title: Euler equations (fluid dynamics)

text: However, we already mentioned that for a thermodynamic fluid the equation for the total energy density is equivalent to the conservation equation:


title: Euler equations (fluid dynamics)

text: Expanding the fluxes can be an important part of constructing numerical solvers, for example by exploiting (approximate) solutions to the Riemann problem. In regions where the state vector y varies smoothly, the equations in conservative form can be put in quasilinear form :


title: Euler equations (fluid dynamics)

text: Obviously this Jacobian does not exist in discontinuity regions (e.g. contact discontinuities, shock waves in inviscid nonconductive flows). If the flux Jacobians formula_82 are not functions of the state vector formula_33, the equations reveals "linear".


title: Euler equations (fluid dynamics)

text: The compressible Euler equations can be decoupled into a set of N+2 wave equations that describes sound in Eulerian continuum if they are expressed in characteristic variables instead of conserved variables.


title: Euler equations (fluid dynamics)

text: In fact the tensor A is always diagonalizable. If the eigenvalues (the case of Euler equations) are all real the system is defined "hyperbolic", and physically eigenvalues represent the speeds of propagation of information. If they are all distinguished, the system is defined "strictly hyperbolic" (it will be proved to be the case of one-dimensional Euler equations). Furthermore, diagonalisation of compressible Euler equation is easier when the energy equation is expressed in the variable entropy (i.e. with equations for thermodynamic fluids) than in other energy variables. This will become clear by considering the 1D case.


title: Euler equations (fluid dynamics)

text: If formula_86 is the right eigenvector of the matrix formula_87 corresponding to the eigenvalue formula_88, by building the projection matrix:


title: Euler equations (fluid dynamics)

text: Since A is constant, multiplying the original 1-D equation in flux-Jacobian form with P yields the characteristic equations:


title: Euler equations (fluid dynamics)

text: The original equations have been decoupled into N+2 characteristic equations each describing a simple wave, with the eigenvalues being the wave speeds. The variables "w" are called the "characteristic variables" and are a subset of the conservative variables. The solution of the initial value problem in terms of characteristic variables is finally very simple. In one spatial dimension it is:


title: Euler equations (fluid dynamics)

text: Now it becomes apparent that the characteristic variables act as weights in the linear combination of the jacobian eigenvectors. The solution can be seen as superposition of waves, each of which is advected independently without change in shape. Each "i"-th wave has shape "w""p" and speed of propagation "λ". In the following we show a very simple example of this solution procedure.


title: Euler equations (fluid dynamics)

text: If one considers Euler equations for a thermodynamic fluid with the two further assumptions of one spatial dimension and free (no external field: "g" = 0) :


title: Euler equations (fluid dynamics)

text: recalling that formula_66 is the specific volume, formula_98 the flow speed, formula_68 the specific entropy, the corresponding jacobian matrix is:


title: Euler equations (fluid dynamics)

text: This determinant is very simple: the fastest computation starts on the last row, since it has the highest number of zero elements.


title: Euler equations (fluid dynamics)

text: This parameter is always real according to the second law of thermodynamics. In fact the second law of thermodynamics can be expressed by several postulates. The most elementary of them in mathematical terms is the statement of convexity of the fundamental equation of state, i.e. the hessian matrix of the specific energy expressed as function of specific volume and specific entropy:


title: Euler equations (fluid dynamics)

text: Then the matrix has three real eigenvalues all distinguished: the 1D Euler equations are a strictly hyperbolic system.


title: Euler equations (fluid dynamics)

text: At this point one should determine the three eigenvectors: each one is obtained by substituting one eigenvalue in the eigenvalue equation and then solving it. By substituting the first eigenvalue λ one obtains:


title: Euler equations (fluid dynamics)

text: The two equations are redundant as usual, then the eigenvector is defined with a multiplying constant. We choose as right eigenvector:


title: Euler equations (fluid dynamics)

text: Finally it becomes apparent that the real parameter "a" previously defined is the speed of propagation of the information characteristic of the hyperbolic system made of Euler equations, i.e. it is the "wave speed". It remains to be shown that the sound speed corresponds to the particular case of an isentropic transformation:


title: Euler equations (fluid dynamics)

text: the soundspeed results always the square root of ratio between the isentropic compressibility and the density:


title: Euler equations (fluid dynamics)

text: where the Feynman subscript notation formula_124 is used, which means the subscripted gradient operates only on the factor formula_34.


title: Euler equations (fluid dynamics)

text: Lamb in his famous classical book Hydrodynamics (1895), still in print, used this identity to change the convective term of the flow velocity in rotational form:


title: Euler equations (fluid dynamics)

text: the Euler momentum equation assumes a form that is optimal to demonstrate Bernoulli's theorem for steady flows:


title: Euler equations (fluid dynamics)

text: In case of a steady flow the time derivative of the flow velocity disappears, so the momentum equation becomes:


title: Euler equations (fluid dynamics)

text: And by projecting the momentum equation on the flow direction, i.e. along a "streamline", the cross product disappears because its result is always perpendicular to the velocity:


title: Euler equations (fluid dynamics)

text: that is the mass conservation for a steady incompressible flow states that the density along a streamline is constant. Then the Euler momentum equation in the steady incompressible case becomes:


title: Euler equations (fluid dynamics)

text: That is, the momentum balance for a steady inviscid and incompressible flow in an external conservative field states that the total head along a streamline is constant.


title: Euler equations (fluid dynamics)

text: The right-hand side appears on the energy equation in convective form, which on the steady state reads:


title: Euler equations (fluid dynamics)

text: Since the external field potential is usually small compared to the other terms, it is convenient to group the latter ones in the total enthalpy:


title: Euler equations (fluid dynamics)

text: That is, the energy balance for a steady inviscid flow in an external conservative field states that the sum of the total enthalpy and the external potential is constant along a streamline.


title: Euler equations (fluid dynamics)

text: By substituting the pressure gradient with the entropy and enthalpy gradient, according to the first law of thermodynamics in the enthalpy form:


title: Euler equations (fluid dynamics)

text: Friedmann deduced this equation for the particular case of a perfect gas and published it in 1922. However, this equation is general for an inviscid nonconductive fluid and no equation of state is implicit in it.


title: Euler equations (fluid dynamics)

text: On the other hand, by substituting the enthalpy form of the first law of thermodynamics in the rotational form of Euler momentum equation, one obtains:


title: Euler equations (fluid dynamics)

text: In the steady case the two variables entropy and total enthalpy are particularly useful since Euler equations can be recast into the Crocco's form:


title: Euler equations (fluid dynamics)

text: From these relationships one deduces that the specific total free energy is uniform in a steady, irrotational, isothermal, isoentropic, inviscid flow.


title: Euler equations (fluid dynamics)

text: The Euler equations are quasilinear hyperbolic equations and their general solutions are waves. Under certain assumptions they can be simplified leading to Burgers equation. Much like the familiar oceanic waves, waves described by the Euler Equations 'break' and so-called shock waves are formed; this is a nonlinear effect and represents the solution becoming multi-valued. Physically this represents a breakdown of the assumptions that led to the formulation of the differential equations, and to extract further information from the equations we must go back to the more fundamental integral form. Then, weak solutions are formulated by working in 'jumps' (discontinuities) into the flow quantities – density, velocity, pressure, entropy – using the Rankine–Hugoniot equations. Physical quantities are rarely discontinuous; in real flows, these discontinuities are smoothed out by viscosity and by heat transfer. (See Navier–Stokes equations)


title: Euler equations (fluid dynamics)

text: Shock propagation is studied – among many other fields – in aerodynamics and rocket propulsion, where sufficiently fast flows occur.


title: Euler equations (fluid dynamics)

text: To properly compute the continuum quantities in discontinuous zones (for example shock waves or boundary layers) from the "local" forms (all the above forms are local forms, since the variables being described are typical of one point in the space considered, i.e. they are "local variables") of Euler equations through finite difference methods generally too many space points and time steps would be necessary for the memory of computers now and in the near future. In these cases it is mandatory to avoid the local forms of the conservation equations, passing some weak forms, like the finite volume one.


title: Euler equations (fluid dynamics)

text: Starting from the simplest case, one consider a steady free conservation equation in conservation form in the space domain:


title: Euler equations (fluid dynamics)

text: where in general F is the flux matrix. By integrating this local equation over a fixed volume V, it becomes:


title: Euler equations (fluid dynamics)

text: Then, basing on the divergence theorem, we can transform this integral in a boundary integral of the flux:


title: Euler equations (fluid dynamics)

text: This "global form" simply states that there is no net flux of a conserved quantity passing through a region in the case steady and without source. In 1D the volume reduces to an interval, its boundary being its extrema, then the divergence theorem reduces to the fundamental theorem of calculus:


title: Euler equations (fluid dynamics)

text: In the one dimensional case the correspondent jump relations, called the Rankine–Hugoniot equations, are:<


title: Euler equations (fluid dynamics)

text: Thanks to the mass difference equation, the energy difference equation can be simplified without any restriction:


title: Euler equations (fluid dynamics)

text: Since the second term is a constant, the Rayleigh equation always describes a simple line in the pressure volume plane not dependent of any equation of state, i.e. the Rayleigh line. By substitution in the Rankine–Hugoniot equations, that can be also made explicit as:


title: Euler equations (fluid dynamics)

text: One can also obtain the kinetic equation and to the Hugoniot equation. The analytical passages are not shown here for brevity.


title: Euler equations (fluid dynamics)

text: describes in general in the pressure volume plane a curve passing by the conditions (v, p), i.e. the Hugoniot curve, whose shape strongly depends on the type of material considered.


title: Euler equations (fluid dynamics)

text: allowing to quantify deviations from the Hugoniot equation, similarly to the previous definition of the "hydraulic head", useful for the deviations from the Bernoulli equation.


title: Euler equations (fluid dynamics)

text: In particular, for Euler equations, once the conserved quantities have been determined, the convective variables are deduced by back substitution:


title: Euler equations (fluid dynamics)

text: It has been shown that Euler equations are not a complete set of equations, but they require some additional constraints to admit a unique solution: these are the equation of state of the material considered. To be consistent with thermodynamics these equations of state should satisfy the two laws of thermodynamics. On the other hand, by definition non-equilibrium system are described by laws lying outside these laws. In the following we list some very simple equations of state and the corresponding influence on Euler equations.


title: Euler equations (fluid dynamics)

text: where formula_50 is the specific energy, formula_66 is the specific volume, formula_68 is the specific entropy, formula_190 is the molecular mass, formula_191 here is considered a constant (polytropic process), and can be shown to correspond to the heat capacity ratio. This equation can be shown to be consistent with the usual equations of state employed by thermodynamics.


title: Euler equations (fluid dynamics)

text: Then for an ideal gas the compressible Euler equations can be simply expressed in the "mechanical" or "primitive variables" specific volume, flow velocity and pressure, by taking the set of the equations for a thermodynamic system and modifying the energy equation into a pressure equation through this mechanical equation of state. At last, in convective form they result:


title: Euler equations (fluid dynamics)

text: In the case of steady flow, it is convenient to choose the Frenet–Serret frame along a streamline as the coordinate system for describing the steady momentum Euler equation:


title: Euler equations (fluid dynamics)

text: where formula_1, formula_12 and formula_37 denote the flow velocity, the pressure and the density, respectively.


title: Euler equations (fluid dynamics)

text: Let formula_201 be a Frenet–Serret orthonormal basis which consists of a tangential unit vector, a normal unit vector, and a binormal unit vector to the streamline, respectively. Since a streamline is a curve that is tangent to the velocity vector of the flow, the left-hand side of the above equation, the convective derivative of velocity, can be described as follows:


title: Euler equations (fluid dynamics)

text: Therefore, the momentum part of the Euler equations for a steady flow is found to have a simple form:


title: Euler equations (fluid dynamics)

text: The second equation expresses that, in the case the streamline is curved, there should exist a pressure gradient normal to the streamline because the centripetal acceleration of the fluid parcel is only generated by the normal pressure gradient.


title: Euler equations (fluid dynamics)

text: Let formula_207 be the distance from the center of curvature of the streamline, then the second equation is written as follows:


title: Euler equations (fluid dynamics)

text: In a steady flow of an inviscid fluid without external forces, the center of curvature of the streamline lies in the direction of decreasing radial pressure.


title: Euler equations (fluid dynamics)

text: Although this relationship between the pressure field and flow curvature is very useful, it doesn't have a name in the English-language scientific literature. Japanese fluid-dynamicists call the relationship the "Streamline curvature theorem".


title: Euler equations (fluid dynamics)

text: This "theorem" explains clearly why there are such low pressures in the centre of vortices, which consist of concentric circles of streamlines.


title: Euler equations (fluid dynamics)

text: All potential flow solutions are also solutions of the Euler equations, and in particular the incompressible Euler equations when the potential is harmonic.


title: Death March to the Parallel World Rhapsody

text: Ichiro Suzuki is a 29-year old game programmer who was tasked with fixing several bugs in two MMORPGs his company is preparing for publication. However, he becomes extremely worn out as he is working during the weekend. After taking a nap, he mysteriously wakes up in a parallel world that resembles some of the fantasy RPG worlds he had worked on, as a 15-year old named Satou, later Satou Pendragon, a nickname he uses while running beta tests, and with what looks like the menu screen of the game he was working on appearing before his inner eye.


text: However, before he can grasp his current situation, an army of lizardmen ambushes him and launches an all-out attack on him. In desperation, he uses all three of his special 'Meteor Rain' attack options (a quick fix he added to the game for new players which kills all enemies in the vicinity) at once and wipes them all out - accidentally killing a god as well. As a result, his level jumps from 1 to 310, maximizing his stats immensely and making him one of the most powerful people in the world. With no way to return to his world, and as a high-leveled adventurer armed with a myriad of different physical, cognitive and magical abilities and weapons, he sets out to uncover the secrets of this new world, earning the trust and affection of many people in the process while keeping his overpowered stats concealed.


text: Hiro Ainana first published "Death March to the Parallel World Rhapsody" as a web novel on the user-generated content site Shōsetsuka ni Narō in 2013, before republishing it as a light novel with illustrations by shri. The first volume was released by Fujimi Shobo in March 2014. Twenty-six volumes have been released to date. North American publisher Yen Press announced its license to the novels on May 20, 2016.


text: Ayamegumu began serializing a manga adaptation in Fujimi Shobo's "Age Premium" magazine in December 2014. "Age Premium" ceased publication with its 49th issue on July 9, 2016, and the manga was one of five titles that were transferred to "Monthly Dragon Age". The manga has been licensed by Yen Press.


text: Akira Segami launched a prequel manga, titled , adapted from the short story by the same name in "Death March to the Parallel World Rhapsody: Ex", in Fujimi Shobo's "shōnen" manga magazine "Monthly Dragon Age" on February 9, 2018. The manga ended on July 9, 2018.


text: A gourmet spin-off manga by Tsurumi, titled "Death March kara Hajimaru Isekai Kōfukukyoku", began serialization in "Monthly Dragon Age" in the February 2022 issue released on January 8, 2022. It centers around the character, Phantom Chef Lulu.


text: An anime adaptation was announced via a wraparound band on the fourth volume of the manga on December 10, 2016. The television series is directed by Shin Oonuma at Silver Link and Connect with scripts written by Kento Shimoyama, while Shoko Takimoto designed the characters. MONACA composed the music at DIVE II Entertainment. The series aired from January 11 to March 29, 2018, on AT-X, with further broadcasts on Tokyo MX and BS11. It ran for 12 episodes and covers the first 3 volumes of the light novel. The opening theme is by Run Girls, Run! while the ending theme is by Wake Up, Girls!. Crunchyroll streamed the series, while Funimation streamed an English dub.


text: The series was the 10th best-selling light novel series in Japan during the first half of 2018, selling 211,393 copies.


title: Transition from Ming to Qing

text: The transition from Ming to Qing, alternatively known as Ming–Qing transition or the Manchu conquest of China, from 1618 to 1683, saw the transition between two major dynasties in Chinese history. It was a decades-long conflict between the emerging Qing dynasty, the incumbent Ming dynasty, and several smaller factions (like the Shun dynasty and Xi dynasty). It ended with the consolidation of Qing rule, and the fall of the Ming and several other factions.


title: Transition from Ming to Qing

text: Leading up to the Qing, in 1618, the Later Jin khan Nurhaci commissioned a document entitled the Seven Grievances, which enumerated grievances against the Ming. Many of the grievances dealt with conflicts against the Ming-backed Yehe clan of the Jurchens. Nurhaci's demand that the Ming pay tribute to him to redress the seven grievances was effectively a declaration of war, as the Ming were not willing to pay money to a former tributary. Shortly afterwards, Nurhaci rebelled against Ming rule in Liaoning.


title: Transition from Ming to Qing

text: At the same time, the Ming dynasty was fighting for its survival against fiscal turmoil and peasant rebellions. Han Chinese officials urged Nurhaci's successor Hong Taiji to crown himself emperor, which he did in 1636, declaring the new Qing dynasty. On 24 April 1644, Beijing fell to a rebel army led by Li Zicheng, a former minor Ming official who became the leader of the peasant revolt and then proclaimed the Shun dynasty. The last Ming emperor, the Chongzhen Emperor, hanged himself from the Zuihuai tree in the imperial garden outside the Forbidden City. When Li Zicheng moved against him, the Ming general Wu Sangui shifted his allegiance to the Qing. Li Zicheng was defeated at the Battle of Shanhai Pass by the joint forces of Wu Sangui and Manchu prince Dorgon. On 6 June, the mainly Han Chinese forces of Dorgon and Wu entered the capital.


title: Transition from Ming to Qing

text: The fall of the Ming dynasty was largely caused by a combination of factors. Scholars have argued that the fall of the Ming dynasty may have been partially caused by the droughts and famines caused by the Little Ice Age. Historian Kenneth Swope argues that one key factor was deteriorating relations between Ming Royalty and the Ming Empire's military leadership. Other factors include repeated military expeditions to the North, inflationary pressures caused by spending too much from the imperial treasury, natural disasters and epidemics of disease. Contributing further to the chaos was a peasant rebellion throughout the country in 1644 and a series of weak emperors. Ming power would hold out in what is now southern China for years, though eventually would be overtaken by the Qing forces.


title: Transition from Ming to Qing

text: Other authors have linked the fall of the Ming with the General Crisis affecting the Spanish Empire under Philip IV, the English Civil War and other polities.


title: Transition from Ming to Qing

text: However, the victory was far from complete as it required almost 40 more years before all of China was securely united under Qing rule. In 1661, the Kangxi Emperor ascended the throne, and in 1662 his regents launched the Great Clearance to defeat the resistance of Ming loyalists in South China. He then fought off several rebellions, such as the Revolt of the Three Feudatories led by Wu Sangui in southern China, starting in 1673, and then countered by launching a series of campaigns that expanded his empire. In 1662, Zheng Chenggong (Koxinga) drove out and defeated the Dutch and founded the Kingdom of Tungning in Taiwan, a Ming loyalist state with the goal of reunifying China. However, Tungning was defeated in 1683 at the Battle of Penghu by Han Chinese admiral Shi Lang, a former admiral under Koxinga.


title: Transition from Ming to Qing

text: The Qing victory was overwhelmingly the result of the defection of the Ming dynasty's Liaodong military establishment and other defectors, with the Manchu military playing a very minor role (see below for specific examples).


title: Transition from Ming to Qing

text: The Manchus are sometimes described as a nomadic people, when in fact they were not nomads, but a sedentary agricultural people who lived in fixed villages, farmed crops, practiced hunting and mounted archery. Their main military formation was infantry wielding bows and arrows, swords, and pikes, while cavalry was kept in the rear.


title: Transition from Ming to Qing

text: Manchus were living in cities with walls surrounded by villages and adopting Han Chinese-style agriculture well before the Qing conquest of the Ming, and there was an established tradition of Han Chinese-Manchu mixing before 1644. The Han Chinese soldiers on the Liaodong frontier often mixed with non-Han tribesmen and were largely acculturated to their ways. The Jurchen Manchus accepted and assimilated Han soldiers who went over to them, and Han Chinese soldiers from Liaodong often adopted and used Manchu names. Indeed Nurhaci's secretary Dahai may have been one such individual.


title: Transition from Ming to Qing

text: In the late Ming dynasty, Ming army units had become dominated by officers who would spend long periods of 10 or 12 years in command instead of the usual practice of constant rotation, and the Central Military Command had lost much of its control over regional armies. "Zongdu Junwu", or Supreme Commanders, were appointed throughout the empire to oversee the fiscal and military affairs in the area of their jurisdiction. In the frontier areas these became increasingly autonomous, and especially in Liaodong, where military service and command became hereditary and vassalage-like personal bonds of loyalty grew between officers, their subordinates and troops. This military caste gravitated toward the Jurchen tribal chieftains rather than the bureaucrats of the capital.


title: Transition from Ming to Qing

text: The She-An Rebellion among the Yi people broke out in Sichuan in 1621 against the Ming, requiring suppression, which was completed in 1629. In the early 1640s, mass rebellions led by many rebel leaders broke out in northwestern China's province of Shaanxi and spread throughout China in the 1640s. Major battles included the sacking of Fengyang by Li Zicheng and Zhang Xianzhong and a battle in Kaifeng which led to the deliberately engineered 1642 Yellow River flood by the Ming governor in an attempt to stop Li Zicheng.


title: Transition from Ming to Qing

text: The Jianzhou Jurchen chief, Nurhaci, is retrospectively identified as the founder of the Qing dynasty. In 1589 the Ming dynasty appointed Nurhaci as paramount chieftain of the Yalu Region, believing that his tribe was too weak to gain hegemony over the larger Yehe and Hada. When the other tribes attacked him to check his power in 1591, he succeeded in defeating them and seized many of their warhorses.


title: Transition from Ming to Qing

text: In 1607 he declared himself "Khan". Upon the advice of an Erdeni, most likely a Chinese transfrontiersman, he proclaimed the Jin State, named after the Jurchen-led Jin dynasty that had ruled over northern China several centuries earlier. His unifying efforts gave the Jurchen the strength to assert themselves backed by an army consisting of majority Han Chinese defectors as well as Ming produced firearms. In May 1618, Nurhaci proclaimed his Seven Grievances against the Ming and departed his capital of Hetu Ala with 20,000 men. The army attacked and captured Fushun, located on the Hun River about 10 kilometers east of Shenyang.


title: Transition from Ming to Qing

text: The Hulun tribes, a powerful confederacy of Jurchen tribes, started recognizing the authority of Nurhaci by the beginning of the 17th century. In some cases, such as with Bujantai of the Ula, chieftains would attempt to reassert their independence and war would break out, but the Jianzhou Jurchens would defeat and assimilate all the tribes eventually (Hada 1601, Hoifa 1607, Ula 1613, Yehe 1619). The powerful Yehe Jurchens under Gintaisi united with the forces of the Ming dynasty to combat the rise of Nurhaci but Gintaisi was defeated and died in 1619. The fur-trapping Warka peoples near the Pacific coast were subjugated as tributary tribes from 1599 to 1641.


title: Transition from Ming to Qing

text: By summer 1621, the Ming's Liaodong fortress cities, Fushun, Shenyang, and Liaoyang, were all handed over to the Later Jin by traitors and defectors. Fushun's commander surrendered after a single attack when promised that his troops and their families would not be enslaved or forced to change any of their customs (including hairstyle), but rather given high office. Shenyang fell with the aid of Mongol Ming soldiers in the city; Liaoyang fell after traitors let down ropes for the Jurchens to climb the wall in the night. The Ming general Li Yongfang who surrendered the city of Fushun in what is now Liaoning province in China's northeast did so after Nurhaci gave him an Aisin Gioro princess in marriage and a noble title. The princess was one of Nurhaci's granddaughters. In April 1625, Nurhaci designated Shenyang the new capital city, which would hold that status until the Qing conquest of Beijing in 1644. In 1625, the Jurchens captured the port city of Lüshun, thus controlling the whole Liaodong peninsula.


title: Transition from Ming to Qing

text: When the Jurchens were reorganized by Nurhaci into the Eight Banners, many Manchu clans were artificially created from groups of unrelated people who would found a new Manchu clan ("mukun") using a term of geographic origin such as a toponym for their "hala" (clan name). The irregularities over Jurchen and Manchu clan origin led to the Qing trying to document and systemize the creation of histories for Manchu clans, including manufacturing an entire legend around the origin of the Aisin Gioro clan by taking mythology from the northeast.


title: Transition from Ming to Qing

text: Nurhaci read the Chinese novels "Romance of the Three Kingdoms" and "Water Margin", learning all he knew about Chinese military and political strategies from them.


title: Transition from Ming to Qing

text: In February 1626, the Jurchens besieged Ningyuan but suffered a defeat in which Nurhaci was mortally wounded.


title: Transition from Ming to Qing

text: The Later Jin had lost at the Battle of Ningyuan the previous year and their khan Nurhaci died from his wounds afterwards. Peace negotiations with the Ming after the battle delayed an aggressive Ming response to the Jurchen loss, and the Ming general Yuan Chonghuan was busy fortifying the border garrisons and training new musketeers. The new khan Hong Taiji was eager for a quick victory to consolidate his position as khan. By invading Joseon he also hoped to extract much-needed resources for his army and subjects, who had suffered in the war against the Ming.


title: Transition from Ming to Qing

text: In 1627, Hong Taiji dispatched princes Amin, Jirgalang, Ajige and Yoto to Joseon with 30,000 troops, under the guidance of Gang Hong-rip and Li Yongfang. The Jurchens met sharp resistance at the border towns but Joseon border garrisons were quickly defeated. The Jurchen army advanced into Uiju where Ming general Mao Wenlong was stationed, and Mao quickly fled with his men into the Bohai Sea. Next, the Jurchens attacked Anju. When it became clear that defeat was inevitable, the Anju garrisons committed suicide by blowing up their gunpowder storehouse. Pyongyang fell without a fight and the Jin army crossed the Taedong River. Joseon Korean King Injo asked the Ming to send cannons and hwagi rocket carts in addition to the Ming "southern army" to help against the 1627 Manchu invasion of Korea as Joseon forts fell and Joseon troops were wiped out.. He also said Korean commoners had to provide excessive rations to Ming general Mao Wenlong.


title: Transition from Ming to Qing

text: By this time news of the invasion had reached the Ming court, which immediately dispatched a relief contingent to Joseon, slowing the Jurchen advance into Hwangju. King Injo then dispatched an envoy to negotiate a peace treaty, but by the time the messenger returned, Injo had already fled from Hanseong to Ganghwa Island in panic.


title: Transition from Ming to Qing

text: The Khorchin Mongols allied with Nurhaci and the Jurchens in 1626, submitting to his rule for protection against the Khalkha Mongols and Chahar Mongols. Seven Khorchin nobles died at the hands of Khalkhas and Chahars in 1625. This started the Khorchin alliance with the Qing.


title: Transition from Ming to Qing

text: The Chahar Mongols were fought against by Dorgon in 1628 and 1635. An expedition against the Chahar Mongols in 1632 was ordered to establish a trading post at Zhangjiakou. The Qing defeated the armies of the Mongol khan Ligdan, who was allied to the Ming, bringing an end to his rule over the Northern Yuan. The defeat of Ligdan Khan in 1634, in addition to winning the allegiance of the Southern Mongol hordes, brought a vast supply of horses to the Qing, while denying the same supply to the Ming. The Qing also captured the Great Seal of the Mongol Khans, giving them the opportunity to portray themselves as heirs of the Yuan dynasty as well.


title: Transition from Ming to Qing

text: Hong Taiji was the eighth son of Nurhaci, whom he succeeded as the second ruler of the Later Jin dynasty in 1626. He organised imperial examinations to recruit scholar-officials from the Han Chinese, and adopted Chinese legal forms. He formed autonomous Han Chinese military colonies governed by Han Chinese officials, where Manchus were forbidden to trespass. Hong Taiji curtailed the power of the Manchu princes by relying on Han Chinese officials. He personally welcomed surrendered Ming commanders, eating side-by-side with them so as to build a rapport that was impossible with the Ming emperors. The Manchus, led by Prince Amin, expressed their displeasure at the situation by massacring the population of Qian'an and Yongping. Hong Taiji responded by arresting and imprisoning Amin, who later died in prison. He then implemented, on the urging of his Han Chinese advisors, Chinese-style Confucian education, and Ming-style government ministries. When Zhang Chun, a Ming commander, was captured but refused to defect, Hong Taiji personally served him with food to show his sincerity (Zhang still refused but was kept in a temple until his death). With the surrender of Dalinghe in 1631, the most capable army officers of the Ming became faithful followers of the new dynasty who would take over the preparation and planning of much of the war. From this episode onward, the Ming-Qing transition ceased to be an inter-nation conflict between Chinese and Manchus but rather a civil war between Liaodong and Beijing.


title: Transition from Ming to Qing

text: Meanwhile, in the Ming, the Wuqiao mutiny broke out in 1631, led by Kong Youde and Geng Zhongming. Undersupplied and underpaid soldiers mutinied against the Ming dynasty. They subsequently sailed across Bohai Gulf and defected to the Jurchens en masse. During the mutiny, they purged thousands of Southern Chinese, suspecting them to be loyal to the Ming.


title: Transition from Ming to Qing

text: Hong Taiji was reluctant to become Emperor of China. However, Han Chinese officials Ning Wanwo, Fan Wencheng, Ma Guozhu, Zu Kefa, Shen Peirui, and Zhang Wenheng urged him to declare himself as Emperor of China. On 14 May 1636, he accepted this advice, changing the name of his regime from the Later Jin to the Qing dynasty, and enthroning himself as Emperor of China in an elaborate Confucian ceremony.


title: Transition from Ming to Qing

text: Hong Taiji's renaming of the Jurchens to Manchus was meant to hide the fact that the ancestors of the Manchus, the Jianzhou Jurchens, were ruled by the Han Chinese. The Qing dynasty carefully hid the two original editions of the books of ""Qing Taizu Wu Huangdi Shilu"" and the ""Manzhou Shilu Tu"" (Taizu Shilu Tu) in the Qing palace, forbidding them from public view, because they showed that the Manchu Aisin-Gioro family had been ruled by the Ming dynasty. In the Ming period, the Koreans of Joseon referred to the Jurchen-inhabited lands north of the Korean peninsula, above the rivers Yalu and Tumen, to be part of Ming China, as the "superior country" (sangguk), the name they used to refer to Ming China. The Qing deliberately excluded references and information from the "History of Ming" that showed the Jurchens (Manchus) as subservient to the Ming dynasty, to hide their former subservient relationship to the Ming. The "Veritable Records of Ming" were not used to source the "History of Ming" because of this. Refusing to mention in the Mingshi that the Qing founders were Ming China's subjects was meant to avoid the accusation of rebellion.


title: Transition from Ming to Qing

text: Han Chinese generals who defected to the Manchus were often given women from the imperial Aisin-Gioro family in marriage. Manchu Aisin-Gioro princesses were also married to Han Chinese officials' sons. The Manchu leader Nurhaci married one of his granddaughters (Abatai's daughter) to the Ming general Li Yongfang after he surrendered Fushun in Liaoning to the Manchus in 1618. The offspring of Li Yongfang received the "Third Class Baron" () title. Li Yongfang was the great-great-great-grandfather of Li Shiyao. The 4th daughter of Kangxi was wedded to Sun Cheng'en, son of the Han Chinese Sun Sike. Other Aisin-Gioro women married the sons of the Han Chinese generals Geng Jimao, Shang Kexi, and Wu Sangui. Meanwhile, the ordinary soldiers who defected were often given non-royal Manchu women as wives, and a mass marriage of Han Chinese officers and officials to Manchu women numbering 1,000 couples was arranged by Prince Yoto and Khan Hong Taiji in 1632 to promote harmony between the two ethnic groups.


title: Transition from Ming to Qing

text: This policy, which began before the invasion of 1644, was continued after it. A 1648 decree from Shunzhi allowed Han Chinese civilian men to marry Manchu women from the Banners with the permission of the Board of Revenue if they were registered daughters of officials or commoners or the permission of their banner company captain if they were unregistered commoners, and it was only later in the dynasty that these policies allowing intermarriage were done away with. The decree was formulated by Prince Dorgon. In the beginning of the Qing dynasty the Qing government supported Han Chinese defectors weddings to Manchu girls. Han Chinese Bannermen wedded Manchus and there was no law against this.


title: Transition from Ming to Qing

text: The "Dolo efu" rank was given to husbands of Qing princesses. Geng Zhongming, a Han Chinese bannerman, was awarded the title of Prince Jingnan, and his son Geng Jingmao managed to have both his sons Geng Jingzhong and Geng Zhaozhong become court attendants under the Shunzhi Emperor and married Aisin-Gioro women, with Prince Abatai's granddaughter marrying Geng Zhaozhong and Haoge's (a son of Hong Taiji) daughter marrying Geng Jingzhong. A daughter of the Manchu Aisin-Gioro Prince Yolo was wedded to Geng Juzhong, who was another son of Geng Jingmao. Aisin-Gioro women were also offered to Mongols who defected to the Manchus. The Manchu Prince Regent Dorgon gave a Manchu woman as a wife to the Han Chinese official Feng Quan, who had defected from the Ming to the Qing. Feng Quan willingly adopted the Manchu queue hairstyle before it was enforced on the Han Chinese population and he also learned the Manchu language.


title: Transition from Ming to Qing

text: When Li Yongfang surrendered, he was given much higher status than under the Ming, and even allowed to keep his troops as retainers. Kong Youde, Shang Kexi and Geng Zhongming were also allowed to keep their personal armies. The warlord Shen Zhixiang, who had unlawfully taken over command of his deceased uncle Shen Shikui's troops as his private army, was unable to attain recognition from the Ming court. He then proceeded to lead his forces to switch allegiance to the Qing, and they became critical assets to the Qing.


title: Transition from Ming to Qing

text: There were too few ethnic Manchus to rule China, but they absorbed defeated Mongols, and, more importantly, added Han Chinese to the Eight Banners. The Manchus had to create an entire "Jiu Han jun" (Old Han Army) due to the very large number of Han Chinese soldiers absorbed into the Eight Banners by both capture and defection. The Qing showed that the Manchus valued military skills in propaganda targeted towards the Ming military to get them to defect to the Qing, since the Ming civilian political system discriminated against the military. From 1618 to 1631 Manchus received Han Chinese defectors and their descendants became Han Bannermen and those killed in battle were commemorated as martyrs in biographies.


title: Transition from Ming to Qing

text: Hong Taiji recognized that Ming defectors were needed in order to defeat the Ming, explaining to other Manchus why he needed to treat the Ming defector general Hong Chengchou leniently. Hong Taiji understood that the Ming would not be easily defeated unless Han Chinese troops wielding musket and cannon were included in the army. Indeed, among the Banners, gunpowder weapons like muskets and artillery were specifically used by the Han Chinese Banners. The Manchus established an artillery corps made out of Han Chinese soldiers in 1641. The use of artillery by Han Bannermen may have led to them being known as "heavy" soldiers (ujen cooha). The "red coat cannon" were part of the Han army (Liaodong Han Chinese) serving the Qing.


title: Transition from Ming to Qing

text: Ming officers who defected to the Qing were allowed to retain their previous military rank. The Qing received the defection of Shen Zhixiang in 1638. Among the other Han Chinese officers who defected to the Qing were Ma Guangyuan, Wu Rujie, Zu Dashou, Quan Jie, Geng Zhongming, Zu Zehong, Zu Zepu, Zu Zerun, Deng Changchun, Wang Shixian, Hong Chengchou, Shang Kexi, Liu Wuyuan, Zu Kefa, Zhang Cunren, Meng Qiaofang, Kong Youde, Sun Dingliao. Aristocratic and military ranks, silver, horses and official positions were given to Han Chinese defectors like Zhang Cunren, Sun Dingliao, Liu Wu, Liu Liangchen, Zu Zehong, Zu Zepu, Zu Kufa and Zu Zerun. Han Chinese defectors were primarily responsible for military strategy after 1631.


title: Transition from Ming to Qing

text: So many Han defected to the Qing and swelled up the ranks of the Eight Banners that ethnic Manchus became a minority within the Banners, making up only 16% in 1648, with Han Chinese Bannermen dominating at 75% and Mongol Bannermen making up the rest. It was this multi-ethnic force in which Manchus were only a minority, which unified China for the Qing. The Qing takeover was done by the multi-ethnic Han Chinese Banners, Mongol Banners, and Manchu Banners which made up the Qing military. In 1644, Ming China was invaded by an army that had only a fraction of Manchus, being multi-ethnic, with Han Chinese Banners, Mongol Banners, and Manchu Banners. The political barrier was between the commoners made out of non-bannermen Han Chinese and the "conquest elite", made out of Han Chinese bannermen, nobles, and Mongols and Manchu. It was not ethnicity which was the factor. Han Chinese (Nikan) bannermen used banners of black color and Nurhaci was guarded by Han Chinese soldiers. Other banners became a minority compared to the Han Chinese (Nikan) Black Banner detachments during Nurhaci's reign.