Over 50 countries fought on the battlegrounds of Asia, Europe, North Africa, the Atlantic and Pacific Oceans, and the Mediterranean Sea in one of the world's most deadly and costliest wars in world history, World War II. The United States entered the war in 1941 after Japanese planes bombed Pearl Harbor, Hawaii on December 7, 1941. Research estimates that during World War II over 2.5 million Negro men registered for the draft, and large numbers of Negro women volunteered to serve in the Army, Army Air Forces, Navy, Marine Corps, and Coast Guard. Although these men and women experienced discrimination and segregation, they served their country with great distinction and made valuable contributions to the war efforts.