Military history of the United States during World War II The
military history of the United States during World War II covers
the war against Japan, Germany and Italy starting with the 7
December 1941 attack on Pearl Harbor. During the first 2 years
of the global conflict, the United States had maintained formal
neutrality, while supplying Britain, the Soviet Union and China
with war material through Lend-Lease, as well as deploying the
US military to replace the British invasion forces in Iceland
(for early US combat activity in the Pacific Theater, see the
Flying Tigers). During the war over 16 million Americans served
in the United States military, with 290,000 killed in action and
670,000 wounded. Key civilian advisors to President Franklin D.
Roosevelt included Secretary of War Henry Stimson, who mobilized
the nation's industries and induction centers to supply the
Army, commanded by Gen. George C. Marshall and the Air Force
under Gen. Hap Arnold. The Navy, led by Admiral Ernest King,
proved more autono