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The Battle Of The Atlantic 1939-1945

HMS Betony, a Flower class corvette, September 1943
MV Empire Maccall, an aircraft carrier converted from a merchant ship, November 1943

Britain's survival during World War Two depended upon the maintenance of the trade routes to North America. On the outbreak of war, the convoy system was adopted to protect merchant ships. The defeat of France in 1940 transformed the effectiveness of the U-boats since they gained bases in the Bay of Biscay much closer to Britain's trade routes. At first many escorts were used to defend Britain against invasion and the U-boats sank large numbers of unescorted ships. As the invasion threat lessened the escorts returned to convoy work.

Initially the Royal Navy lacked sufficient convoy escorts and air cover was almost non-existent. Large numbers of 1,000 ton coastal escorts, 62 metres long and based on a whalecatcher design were built. Despite their small size these Corvettes were used as ocean escorts but were very uncomfortable in heavy weather. They carried a 102mm gun and up to seventy two depth charges. The Corvettes played a key role in the Battle of the Atlantic. In 1942 ocean going escorts called Frigates, 1,400 ton ships just over 90 metres long and capable of 20 knots, were introduced.

In 1941 more ships were placed in convoys, now escorted all the way across the Atlantic. Advances in radio intelligence and code breaking allowed these convoys to be routed around the U-boats. The German effort was largely contained until the USA entered the war and delays in introducing coastal convoys off the American coast and in the Caribbean boosted losses once more. Convoys were introduced to solve this problem and, by late 1942, the U-boats returned in larger numbers to the mid-Atlantic. They were searching for weaknesses in convoy defences that could be exploited by 'wolf packs' of U-boats.

The Battle of the Atlantic, as it became known, now rose to a peak. Britain had lost the ability to decrypt U-boat signals but, in any case, there were too many U-boats to avoid. The Germans concentrated their wolf packs where air cover was not available, the 'black hole' in mid-Atlantic.

A combination of factors finally tilted the balance against the Germans. The British again broke the German codes so they could concentrate escorts around threatened convoys. Most importantly the RAF agreed to the Admiralty's demands for very long range Liberator maritime patrol aircraft to support the escorts in the 'black hole'. Small escort carriers were also deployed to protect convoys.

The German offensive was failing and on 23 May 1943 the Germans withdrew their U-boats from the Atlantic campaign. This withdrawal was only temporary but later German efforts were broken by the now formidable escort forces. The Battle of the Atlantic had been won. By the end of the war the losses suffered by both sides were appalling. The Allies lost 30,000 seamen and 2,500 merchant ships were sunk. More than 28,000 German submariners were killed and 781 U-boats destroyed.