germany boat built imperial_german_navy shortly world war type class submarines boats german service equipped diesel engines built october imperial shipyard danzig armed torpedo tubes single deck gun second added career september submarine sink ship self propelled torpedo destroyed cruiser hms sank transports english channel later year accordance cruiser rules effect early transferred mediterranean_sea support ottoman_empire anglo french attacks shortly arrival sank british battleships hms triumph bombarding ottoman positions gallipoli successes followed mediterranean including sinking french armored cruiser february served austro hungarian navy germany war italy legally attack italian warships german flag returned germany march join commerce war british maritime trade withdrawn line service employed training submarine new crews survived war sank tow british warship design meters long overall beam height displaced metric tons long tons short tons surfaced long tons short tons submerged boat propulsion system consisted pair cylinder stroke diesel engines manufactured man use surface electric double motor built use submerged sister boats german submarines equipped diesel engines electric motors powered bank cell batteries cruise speed knots mph surface knots mph submerged steering controlled pair forward pair aft single rudder armed centimeter torpedo tubes supplied total torpedoes pair located bow stern initially fitted machine gun use surface end replaced gun second gun added crew officers enlisted sailors service history built imperial shipyard danzig poland laid launched february fitting work completed commissioned fleet october north_sea operations outbreak world war august based island german bight commanded captain lieutenant early august took patrol found british vessels august went second patrol time company sister boats northern north_sea norway scotland patrol attempt locate british blockade line gather intelligence spotted single cruiser destroyer norwegian coast attempted enter forth major royal_navy fleet base later month unsuccessful september encountered british scout cruiser isle surfaced boat batteries spotted smoke funnels horizon submerged attack turned away patrol line hope cruiser submerged broke chase resumed batteries shortly reversed course headed attack position fired single torpedo hit aft conning tower torpedo detonated cruiser magazines destroyed ship large explosion british able lower single sank survivors found wreckage torpedo boats rushed scene warship sunk modern submarine total sailors killed attack caught french steamer november forcing ship stop examining cargo manifest ordered crew abandon ship sank deck gun success came days later british sank accordance cruiser rules governed commerce raiding ships vessels sunk restricted german submarine offensive british french merchant shipping january took boat dover barrage channel turning shelled airfield coastal battery quickly forced withdraw day stopped evacuating crew germans sank charges later day stopped sank cases adhered prize rules including passing pick ships crews successes withdrew area avoid british patrols arrive aftermath passing dover barrage cruised wilhelmshaven mediterranean april transferred mediterranean_sea support germany ally turkey left kiel april leg voyage germany austria-hungary took eighteen days took submarine north scotland avoid dover patrols supply ship refuel unfortunately germans carried poor quality crude oil burned boat diesel engines half fuel supply remaining halfway voyage austria-hungary forced run boat surface conserve fuel increased risk detection allied forces route germans managed escape patrolling british french torpedo boats transport ships reported location finally arrived long tons short tons fuel left tanks left germany long tons short tons spent week austro hungarian submarine bases mid visited austro hungarian boat commander german submarines joined following months calls assistance ottoman ground forces gallipoli peninsula taking heavy casualties allied warships boats included arrived operational area gallipoli day encountered british pre dreadnought battleship brought boat yards target fired single torpedo hit triumph sinking battleship escape destroyers hunting took boat sea floor wait allied forces abandon chase hours sea floor surfaced batteries bring fresh air attacked sank second battleship time british attempted protect torpedo nets small ships able aim torpedo defenses majestic sank span minutes successes brought significant allied capital ships withdrawn protected unable bombard ottoman positions peninsula successes crew awarded kaiser received germany highest award sinking majestic took submarine refuel turkish port attempting dangerous route dardanelles constantinople straits nearly pulled germans managed escape arriving ottoman capital crew given large welcoming ceremony attended required significant maintenance crew given month shore leave repairs carried repair work finished sortied dardanelles patrol spotted allied munitions ship sank single torpedo later patrol allied spotted germans crash dive escape rammed brought minefield exploded boat stern caused significant damage able withdraw constantinople moved black_sea served nucleus newly formed september undertook patrol eastern mediterranean meantime allies finally managed establish complete blockade dardanelles mines nets prevent submarines operating constantinople unable return constantinople instead took boat germany formal state war italy august result german boats legally attack italian ships despite fact italy war austria-hungary restriction german submarines operating mediterranean commissioned austro hungarian navy german crews remained aboard following arrival commissioned austro hungarian served italy declared war germany august meantime began successes allied maritime trade february sank british steamer france week later torpedoed sank french armored cruiser syrian coast cruiser sank quickly heavy loss life men went ship spring patrolling sicily encountered allied ship auxiliary cruiser disguised unarmed merchant ship fired shot ship bow refused stop returned fire small deck gun decided close sink ship revealed heavy armament wounded shell splinters withdrew submarine cover smoke screen april sank british steamer city sank small italian sailing vessels october october sent long ton steamship days italian ships small sailing vessels sunk sicily december torpedoed british steamer east crete ship managed reach alexandria return north_sea early recalled germany join submarine warfare campaign waged britain route stopped sank pair british sailing vessels february pair portuguese sailing ships day february sank french steamer days later finished dutch steamer damaged submarine february seven ships followed day included dutch norwegian steamer patrol late april caught ships norwegian april april russian april russian vessel followed british sunk respectively swedish baltic proved victory sunk june attacked convoy merchant ships escorted fourteen destroyers august south west ireland took escorting destroyers briefly gauge speed course transports firing torpedoes diving reported torpedoes hit destroyers immediately rushed begin depth charge attacks hour hunt destroyers withdrew rejoin convoy experience led change tactics future attacks escorted convoys instead attacking ships far away possible chose fire torpedoes closer range dive transport ships destroyers unable launch depth charges fear damaging transports assigned iii boat flotilla later submarine training boat new crews survived war february accidentally sank north_sea tow britain formally surrendered course commerce raiding sank ships combined gross register tons grt damaged total gross register tons grt ships sunk included battleships cruisers summary raiding history
SM U-21 (Germany)