Atlantic, Battle of the

During World War II, continuous battle fought in the Atlantic Ocean by the sea and air forces of the Allies and Germany, to control the supply routes to the UK. It is estimated that the Allies destroyed nearly 800 U-boats, and at least 2,200 convoys (75,000 merchant ships) crossed the Atlantic, protected by Allied naval forces.

At the outbreak of war, Germany had 57 U-boats, with 22 available for immediate service in the Atlantic; a further 1,174 U-boats were commissioned during the war. The battle opened 4 September 1939, the first night of the war, when the ocean liner Athenia, sailing from Glasgow to New York, was torpedoed by a German U-boat off the Irish coast. The Germans employed a variety of tactics in the course of the campaign such as U-boats, surface-raiders, indiscriminate minelaying, and aircraft, but the Allies successfully countered all of them, although they suffered some significant reverses such as the sinking of the armed merchant ships Rawalpindi (23 November 1939) and Jervis Bay (5 November 1940) by German warships.

U-boats remained the greatest menace to Allied shipping, especially after the destruction of the German battleship Bismarck by the British on 27 May 1941.

Prior to the US entry into the war in 1941, destroyers were supplied to the British under the Lend-Lease Act.