The Battle of the Atlantic was the longest continuous military campaign of World War II, running from 1939 through the defeat of Nazi Germany in 1945, and was at its height from mid-1940 through to about the end of 1943. The campaign pitted the German Navy’s surface raiders and U-boats against Allied convoys from North America and the South Atlantic to the United Kingdom and Russia, protected mainly by the British and Canadian navies and air forces, later aided by United States ships and aircraft. The German U-boats were joined by Italian submarines after Italy entered the war in June 1940.