Battle of the Atlantic
Churchill called the Battle of the Atlantic 'the dominating factor all through the war' — the only thing that ever truly frightened him. If Germany succeeded in cutting the Atlantic sea lanes, Britain could not be supplied with food, fuel, and materiel from North America and the Empire; without supply, Britain could not continue fighting; without Britain as a base, the United States could not deploy forces in Europe. The battle was the strategic foundation of everything else. Germany began its U-boat campaign on the day war was declared, sinking the liner SS Athenia on 3 September 1939. The campaign went through distinct phases. The 'Happy Time' (1940–41) saw U-boats devastating Allied shipping with minimal losses, as Axis forces had access to French Atlantic ports after France's fall and Allied anti-submarine warfare was underdeveloped. In mid-1940, U-boats were sinking 300,000–400,000 tons of Allied shipping per month. The situation improved after the US entry into the war enabled the convoy system to be extended and American destroyer escorts to join the battle. But the second 'Happy Time' (January–August 1942) occurred along the American east coast, where shipping was not yet in convoys; U-boats sank 3.1 million tons in eight months. The decisive technological battle occurred on multiple fronts. Britain's decryption of German naval Enigma messages (the 'Ultra' secret) allowed convoys to be routed around U-boat patrol lines when the codes were readable, but was interrupted by German naval Enigma upgrades in early 1942 that blinded Allied intelligence for ten months. Allied developments included centimetric radar (carried by aircraft) that U-boats could not detect, the Leigh Light (enabling night attacks on surfaced submarines), very long-range aircraft that closed the 'Air Gap' in the mid-Atlantic, and hunter-killer escort carrier groups. May 1943 — 'Black May' — was the turning point: U-boats sank 41 Allied ships but lost 41 submarines to Allied countermeasures in a single month. Admiral Dönitz withdrew the U-boats from the North Atlantic on 24 May 1943. Though the campaign continued until Germany's surrender, the strategic threat to Allied Atlantic supply lines was broken.
- Year: 1939 CE
- Category: Military
