Recounts the role of the United States in World War II at sea, from encounters in the Atlantic before the country entered the war to the surrender of Japan.

The tenth volume in Samuel Eliot Morison's series focuses on the war on enemy submarines in a conflict fought up and down the Atlantic coast from Nova Scotia to Brazil. Allied shipping was in a desperate situation in 1942, as the Germans were building U-boats faster than the British and the Americans could sink them. By summer of 1943, however, the tide had turned, and Germany had lost the strategic initiative in the Atlantic because of the anti-submarine offensive launched by the Western Allies.