The German invasion of Poland on 1 September 1939 led to British and French declarations of war two days later, but Britain's war aim was to end the Nazi menace, not to preserve the status quo in Eastern Europe. This aim endured through a succession of military disasters and the extension of the war to the Mediterranean and the Far East through the intervention of Italy on 10 June 1940 and of Japan on 7 December 1941. From the French armistice with Germany on 22 June 1940 to Hitler's invasion of the Soviet Union exactly a year later the British Commonwealth and Empire fought alone. Hopes of victory depended upon supplies of food, raw materials and munitions from the United States, and therefore on victory over the U-boats as well as on American aid through the Lend-Lease Act of March 1941. Although the Japanese attack on Pearl Harbor brought the United States fully into the war, it was not until the American naval victory at Midway in June 1942 that the Japanese were decisively checked. The summer of 1942 was the nadir of British fortunes: Singapore had surrendered on 15 February; India was threatened. The Commonwealth armies in North Africa were heavily defeated by the Germans and Italians, and it seemed that Egypt too might be lost. The tide turned in late 1942, with the battle of El Alamein (23 October – 5 November), the Anglo-American landings in North Africa (8 November) and the Soviet relief of Stalingrad (19–25 November).