Lasting in effect the whole of the 2nd World War, this was a bloody struggle between the Allies and the German Navy and included airpower on both sides. It was all about control of the shipping routes to Britain.
When the War began in 1939 the Germans had just four battleships plus three ‘pocket’ or smaller battleships, four heavy and six light cruisers. The British, largely due to the efforts of Churchill and others, had eighteen battleships, ten aircraft carriers, fifteen heavy and sixty-two light cruisers.
At first, the Germans used their capital ships as raiders of commercial shipping, and achieved small success but heavy losses. One of the pocket battleships Graf Spee was chased to Uruguay and had to be scuttled in the harbour at Montevideo. Then the mighty Bismarck was sunk by incredibly brave action by torpedo-carrying light aircraft piloted by the Royal Navy’s Fleet Air Arm. Every aeroplane was lost in the assault but Bismarck was put out of the War in the Norwegian fiords, and Hitler decided to keep the rest of the battle fleet in comparative safety in French and Scandinavian ports.
But Britain’s supply lines depended entirely on the sea, and the new German submarines were operating in the Atlantic from 1940, based mainly in Vichy French ports. The unterseeboots were greatly successful, and thousands of tons of shipping were lost to the deadly torpedoes, as well as thousands of lives, those of the daring merchant seamen who manned the almost entirely unarmed merchant ships. They sailed in convoys, which could be protected by the Navy only a distance of four or five hundred miles off the coast of Ireland. A little later, British bases were secured in Iceland, which meant that the convoys had protection up to 1,200 miles. It was May, 1941.
By now the British had a form of underwater radar called Asdic, which was efficient and accurate, but could only work against submarines. The latter moved at night and on the surface, commanded by Germany’s crack sailors. In fact the subs frequently assaulted the convoys at night, and from a position on the surface!
Another threat to the convoys was the German long-range Condor bomber, mostly operating from Brest. The German naval commander-in-chief was Admiral Doenitz, a non-Nazi with sincere admiration for the British Navy and barely controlled distaste for Hitler. It was Doenitz who organised his submarines, E-Boats and aircraft into what he called ‘wolf packs’, attacking convoys with devastating effect. 1942 was the worst year for Allied shipping; in the month of November alone more than 725,000 tons were destroyed.
But then it was 1943 and new tactics and inventions ended the submarine’s dominance. Short-wave radar was the most important of the new devices. It could pick up U-boats on the surface, meaning that they could be located by day or night, and would be forced to spend more valuable time submerged. Also there was high-frequency direction finding, indicating where submarines from the sounds they emitted. By the middle of the year this was standard equipment in all escort vessels. Long-range aircraft which could patrol a thousand miles or so from their bases hunted the U-boats and if one was found, it was usually destroyed by accurate bombing. Aircraft carriers also accompanied the convoys, and from them the Fleet Air Arm joined in the hunting and killing. Engineers and designers had perfected the depth charge, deadly enemy of all submarines, which could be hurled ahead of attacking vessels.
By May/June 1943 Admiral Doenitz told Hitler (who did not want to know) that the Battle of the Atlantic must be called off, or at least postponed, as U-boat losses were above 30% of those at sea. Between June and September not one Allied ship was sunk by German submarines in the Atlantic. Determined not to be outdone, the Germans introduced the ‘schnorkel system’, by which underwater craft could ‘breathe’ when submerged, but between January and June 1944 a million US soldiers and nearly 2 million tons of war materiel crossed the Atlantic practically without loss. The German U-boats bravely carried on with the hopeless battle, though expectation of return to base was almost zero. By the end of the War 781 out of the 1200 U-boats built had been sunk, usually with total loss of the crew. But 2,500 Allied vessels were also destroyed during the Battle of the Atlantic.