This is a list of some of the submarines of the Second World War.Germany used submarines to devastating effect in the Battle of the Atlantic, where it attempted to cut Britain's supply routes by sinking more merchant ships than Britain could replace. While U-boats destroyed a significant number of ships, the strategy ultimately failed. Although U-boats had been updated in the interwar years, the major innovation was improved communications and encryption; allowing for mass-attack naval tactics. By the end of the war, almost 3,000 Allied ships (175 warships, 2,825 merchantmen) had been sunk by U-boats.