The sneak attack on Pearl Harbor in 1941 was a disaster, yet the U.S. had unmatchable advantages with its enormous industrial industrial capacity and citizens willing to meet every need. Armed forces swelled overnight; the most remarkable growth being in air power.
Alllied strategists adopted a policy of winning the war in Europe before launching an all-out offensive against Japan. Heroic U. S. navy and marine fighters held Nipponese forces at bay until the beginning of 1945. By then, island after island was being captured; moreover, a 20th Air Force was established with B-29s--Superfortresses--making disastrous fire raids against the Japanese homeland.
Scientists and engineers were able to construct an atomic bomb and carry out a successful test in New Mexico, convincing American leaders that A-bombs were feasible military weapons, and two such missiles dropped on Japan brought an end to WW II..