Military history of the United States during World War II Military history of the United States during World War II The military history of the United States in World War II covers the war against Germany, Italy, and Japan, starting with the 7 December 1941 attack on Pearl Harbor. During the first two years of World War II, the United States had maintained formal neutrality as made official in the Quarantine Speech delivered by U.S. President Franklin D. Roosevelt in 1937, while supplying Britain, the Soviet Union, and China with war materiel through the Lend-Lease Act which was signed into law on 11 March 1941, as well as deploying the
War crimes in occupied Poland during World War II at Chełmno according to postwar verdict by West Germany, although up to 340,000 victims were estimated by the Polish Main Commission for Investigation of German Crimes in Poland (GKBZNwP), a predecessor of the Institute of National Remembrance. Following the Wannsee Conference of 1942, as part of highly secretive Operation Reinhard in occupied Poland, the German government built three regular killing centres with stationary gas chambers. It was the most deadly phase of the Final Solution, based on implementing semi-industrial means of killing and incinerating people. The new facilities included Treblinka extermination camp (set up in July 1942), Bełżec (March 1942),