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ANTONY PRESTON, JOHN BATCHELOR
Two factors combined to frustrate the Allies' efforts to beat the U-Boat offensive in 1942. The first was the Americans' virtual withdrawal of their escort forces from the Atlantic in June 1942, because these were needed for the Pacific against the Japanese. The second factor was the need to earmark escorts for the large convoys which would be needed for the invasion of North Africa, "Operation Torch". Although they were still responsible for coastal escort work, the American ships retained in the Atlantic now formed 2 per cent of the escort forces available, with the British and Canadians sharing the burden in a 50:48 ratio. This dilution of effort was unavoidable, but it gave the U-Boats a chance to inflict even heavier losses than they might have done, when the escorts were at full stretch.
To counterbalance this problem the large number of escort vessels coming into service did allow the British to organise the first experimental support group in September 1942. This was a group of escorts which operated independently in search of U-Boats, but kept itself at readiness to go to the aid of a hard-pressed convoy. It should not be confused with the old-style hunting groups, because it was based on the convoy system rather than being a replacement for it. The basic idea was to leave the convoy's escort to look after the close-range defense, while the support group could pursue and harry U-Boats to destruction. All too frequently a convoy escort had to leave ii promising contact because she had to return to the convoy, and the support group idea promised to increase the number of sinkings. This is exactly what happened, particularly because support groups were able to operate in the areas where U-Boats were concentrated.
At the start of 1943 both sides were in a strong position. The U-Boats were well led and their achievements in 1942 meant that officers and men were experienced. Against them were ranged a growing force of aircraft and ships equally determined and skilled. Behind both antagonists were the designers and scientists, whose influence would prove decisive.
The first round went to the U-Boats in March. Acting on intelligence gathered after German cryptanalysts broke into the British convoy cypher, Admiral Dönitz arranged a heavy concentration of U-Boats against two eastbound convoys. This led to a successful interception, by a total of 39 U-Boats, of the slow convoy 5C-122, totalling 52 ships, and the faster HX-229, with only 25 ships. Finding the fast convoy first, the U-Boats were able to sink eight ships in a space of less than eight hours. The slow convoy fared rather better when another group of U-Boats attacked, but one U-Boat, U338, was able to sink four merchant ships with five torpedoes. During the next three days the convoys were joined to give their escorts a chance to fight back, but even this did not prevent the U-Boats from sinking another nine ships. In all 140,000 tons of shipping had been sunk, for the loss of only three U-Boats.
This great convoy battle marks the high point of the U-Boat offensive. Dönitz almost achieved his dream of making the convoy system unworkable, for the immediate reaction at the Admiralty was to consider the reintroduction of independent sailings until fresh counter-measures could be devised. At no time did Hitler come closer to victory, for if his U-Boats had cut communications between Britain and North America, not only would the British have been starved into impotence, but he would have been free to turn his whole might against Russia. Fortunately March 1943 was the turning point, and the U-Boats were shortly to receive their most devastating setback.
German Type XXI. The famous "Electro-submarine" designed in 1943 in a desperate attempt to win back the initiative in the Battle of the Atlantic. The Type XXI introduced ideas which influenced all post-war submarine design, including a streamlined hull, rapid reloading for the torpedo-tubes and enlarged battery capacity. By adopting prefabrication Admiral Dönitz hoped to put the Allies back on the defensive by 1944 but production difficulties were never overcome, and only a handful were ready at the surrender in 1945. Displacement: 1,621 tons. Armament: Six 21-in torpedo-tubes (23 torpedoes carried); four 30-mm or 20-mm AA guns. Speed: 15,5 knots (surfaced) , 16 knots (submerged)
The first gleam of hope for the Allies was the intervention' of escort carriers and support groups, which had been held back to cover "Operation Torch". With that landing successfully achieved, all the vital ships and aircraft which had been taken away from the Atlantic were now thrown back into the battle. Then President Roosevelt intervened to make 61 VLR Liberators available to the RAF, a welcome reversal of policy. But the scientists made the biggest contribution, for they had perfected a shortwave radar set for use in aircraft, the ASV (Air to Surface Vessel) set. ASV transmissions could not be picked up by the U-Boats' existing radar receivers, and losses to aircraft attack rose alarmingly. In May another great convoy battle was fought, but this time aircraft and two support groups intervened, with the result that eight out of twelve U-Boats were lost. It was in a frantic effort to find an answer to this unexpected reversal of fortune that the U-Boat Command committed two fundamental blunders.
Basing his calculations on the premise that the Metox receiver would give ample warning of any radar-assisted attack, Dönitz decided that submarines could meet aircraft on equal terms provided that each U-Boat had its anti-aircraft armament increased. Conning tower platforms were extended, and a variety of weapons was added forward and aft. The common weapon was the 2-cm Flak "vierling", a deadly four-barrelled automatic weapon, but single 2-cm and 37-mm weapons were also added, and twin 2-cm. As the main opponents were Sunderland flying boats and Liberator bombers, neither of them very fast or manoeuvrable aircraft, such an array of guns made a surfaced U-Boat an ugly customer, particularly when air crew were not expecting her to stay on the surface to fight it out.