On December 7, 1941, Japan attacked the United States Pacific Fleet at Pearl Harbor, Hawaii, killing thousands and destroying U.S. military ships and planes. Congress declared war against Japan the following day. At the end of the war, after seven military and presidential investigations had identified different reasons for the lack of U.S. preparedness at Pearl Harbor, Congress created a joint committee to review possible lapses in intelligence. Its findings led Congress to pass the National Security Act of 1947 to modernize national security agencies and coordinate military readiness.