The Raid on Dieppe

With America’s entry into the war, Admiral Doenitz’ sent all of his available long range Type IX U-boats to sink merchantmen along the unprepared and nearly undefended East Atlantic coast. The British knew this was happening through the Ultra intercepts, but the Americans ignored them. So began the “Second Happy Time”, as U-boat captains sank ships off the American coast and in the Caribbean Sea with impunity.

The German Kriegsmarine’s (Navy) Happy Time of the first eight months of 1942 wasn’t necessarily destined to be so happy just because of American arrogance and laxity; the Battle of the Atlantic got exponentially more difficult for the Allies on 1 February 1942. On that day, the Kriegsmarine switched from a three rotor to a much more secure four rotor Enigma machine for their U-boats’ operational communications. When Alan Turing and the boys and girls of Hut 8 at Bletchley Park woke that morning, they found they could no longer read the Germans’ mail. Undetected U-boats went about slaughtering the vital merchantmen needed to keep Britain in the war.

Turing needed a four rotor Enigma machine, or at least as much German cryptographic material as possible, such as code books or old messages (these were a source of “cribs” or known plaintexts with their corresponding ciphertext, that dramatically reduced the time needed to decode messages) if Britain and America were going to go back to evading the U-boats and attacking them, instead of chasing them around by following the trail of sunken ships they left behind.

The task to “pinch” i.e. steal, a four rotor Enigma machine fell to the commandos of Lord Louis Mountbatten’s Combined Operations Headquarters. Mountbatten’s normal targets for enemy cipher material were German weather trawlers in the North Atlantic, but they dried up when the Germans established their secret weather stations in Spitsbergen Islands in the Arctic Ocean. The commandos came to rely on sensitive material they captured on various raids to fill the void, such as the Loften and Vargas Islands in Norway, and St Nazaire in France, but none produced what Turing needed, including several other operations planned specifically to pinch a machine but were aborted for various reasons.

In early April 1942, Britain’s clandestine secret service, MI6, and its research arm, the blandly named Inter Service Topographical Department (ISTD) identified a four rotor machine and a veritable treasure trove of cipher material in the Moderne Hotel at the French port of Dieppe. The Moderne housed a Kriegsmarine port headquarters, a headquarters for a squadron of minelayers, and most importantly, a detachment from the Kriegsmarine Special Purpose Signals Regiment 618. MI6 even pinpointed the location of the Enigma machine: locked in a safe in a storage room in the basement.

Mountbatten gave the operation to raid the Moderne Hotel at Dieppe to the “Authorized Looters of the Admiralty”, Ian Fleming’s (author of the James Bond novels) 30 Intelligence Assault Unit. 30AU was a covert intelligence gathering formation that “cleaned up” after, or during, regular and commando operations, and then went out of their way to hide the fact that they did so, so as to preserve the integrity of the information they acquired. Combined Operations planned Operation Sutter using 30AU supported by 40 Royal Marine Commando for June. But several attempts in June and July failed due to bad weather. Sutter was scrapped, and Mountbatten was told to pinch another machine somewhere else.

However, the plan was resurrected in late July by Winston Churchill. Mountbatten considered Churchill his direct superior, much to the General Staff’s dismay. Churchill was fascinated by commandos, cryptanalysis, cloak and dagger stuff in general, and even by Mountbatten, whom he considered a younger version of himself. Operation Sutter was the combination of all of these and Churchill couldn’t resist. Furthermore, Mountbatten was “growing his empire” with the Prime Minister’s support and his operations were getting progressively larger. He still wanted, and needed, to execute Sutter, but the security risks caused by aborted attempts meant that it had to change. So instead of just 30AU and 40 RM Commando, he’d use a whole division. Mountbatten wanted to “crack a nut with a steam hammer” to cover up the true objective in the Moderne Hotel.

Mountbatten wanted the Royal Marine Division but Churchill was under intense political pressure to get the 2nd Canadian Division into the fight. They arrived in Britain just after the evacuation at Dunkirk and had been training for almost two years and had not seen any action. Operation Sutter was renamed Operation Jubilee and the 2nd Canadian Division would provide the steam hammer.

Operation Jubilee was the first Allied large scale division-sized amphibious operation in the European theater. As the US Marines were finding out at that moment in the Solomons, it was much more difficult and complicated than at first realized, especially since the Canadians and commandos weren’t assaulting mostly unoccupied beaches, but a heavily fortified port. The plan called for independent commandos to first clear heavy gun emplacements on the flanks of Dieppe. The next wave of Canadian infantry was to clear machine gun nests and pillboxes overlooking the main assault beaches. The Canadian main body would follow on with a frontal assault supported by tanks on Dieppe itself. While the engineers accompanying the main assault were wrecking the port facilities (the stated cover objective for the raid) 30AU and 40 RM Commando was supposed to secure the hotel and seize the Enigma machine. For the job, 30AU even recruited a former cat burglar and safecracker, given amnesty for his previous crimes, specifically for the mission. In addition to an entire division, this single individual was supposed to be supported by copious amounts of naval gunfire and RAF bombers. However, the bombers were called off as they were too inaccurate and they couldn’t risk damaging the hotel. The supporting battleships and cruisers were also called off in the name of security: the Germans would certainly wonder what they were doing when they entered the English Channel.

At 3 am on 19 August 1942, the invasion force left the south of England to raid Dieppe to “help relieve the pressure on the Soviets and open the second front against the Germans in the West”, which we know now was complete bullshit. Unfortunately, the invasion force didn’t even get across the English Channel before things started to go wrong.

The landing craft of No 3 Commando, charged with silencing the coastal battery at Berneval to the east of the main landings, ran into a small German coastal convoy, whose armed trawler sank or scattered most of their landing craft. However, a handful of the indefatigable commandos managed to land and prevent the guns from firing by sniping at gunners. They accomplished their mission but it was an inauspicious start to the operation.

Further west was the only bright spot of Jubilee. No 4 Commando under the indomitable Lord Lovat, and accompanied by 40 Americans of the newly formed US Army Rangers, “in a classic operation of war” seized and neutralized the battery at Varangeville. The rest of the operation was a disaster.

When the next wave of Canadians came ashore to clear the German positions covering the main assault beaches, the Germans were already alerted and waiting for them in previously unidentified caves and firing positions. The Canadians were massacred and accomplished none of their objectives. Shortly thereafter the main assault landed directly into the teeth of the German defenses. Naval gunfire by destroyers off shore and air support by fighters and fighter bombers was completely inadequate. The few tanks that made it to shore were either stuck in the sand or stopped by roadblocks from getting into town. The engineers needed to blow the barriers were easy targets for German machine gunners. Few Canadians reached the town, much less the hotel. Maj Gen John Roberts, the commander of the 2nd Canadian Division, ordered in his reserve and then 30AU and 40 Commando to force their way in. But after three unsuccessful and very costly assaults, the order went out to evacuate.

Of the 5000 men, mostly Canadians, that took part on the Raid of Dieppe, 900 were killed, 600 wounded, and almost 2000 were captured. Dieppe was a national disaster for Canada. The Germans were genuinely confused about why the Allies would try to force a division sized landing against two full regiments in a fortified city, or even conduct an operation that was “too large for a raid and two small for an invasion”.

They wouldn’t know the answer for seven decades until a curious Canadian historian came across a single recently declassified signals intelligence document from the ISTD that simply stated, “Dieppe Objective Not Realized”, and then unraveled from there.

Mountbatten and Churchill would both maintain the fiction til the day they died that the Raid on Dieppe was a large scale rehearsal for the future amphibious invasion of France. To that end, Dieppe did provide plenty of lessons learned in large scale amphibious operations, in particular naval and air fire support, beach composition and reconnaissance, simplicity of concept and simultaneity of concurrent objectives, among many others. These lessons would be directly incorporated into and instrumental in the success of the Operation Torch landings in North Africa in November of 1942. But the cost for those lessons, and that fiction, was high: in addition to the casualties, Roberts would be made a scapegoat, and the Germans would bask propaganda value of the Allied defeat for months.

As for the original objective of the Dieppe Raid, the four rotor Enigma machine? Turing would have to wait another two months when one fell into the figurative Allied lap after a chance capture of sinking U-boat off Egypt in October.

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