<P> The United States Navy grew rapidly during World War II from 1941--45, and played the central role in the war against Japan . It assisted the British Royal Navy in the naval war against Germany and Italy . The largest amphibious invasion of all time was the invasion of France in June 1944 . The combatant warships were 79 percent British or Canadian, 17 percent American, and the remainder from other Allies . </P> <P> The U.S. Navy grew slowly in the years prior to World War II . International naval limitations on operation in the 1920s . Battleship production restarted in 1937, commencing with the USS North Carolina (BB - 55). It was able to add to its fleets during the early years of the war while the US was still neutral, increasing production of vessels both large and small, deploying a navy of nearly 350 major combatant ships by December 1941 and having an equal number under construction . </P> <P> The Imperial Japanese Navy (IJN) sought naval superiority in the Pacific by sinking the main American battle fleet at Pearl Harbor, which was built around its battleships . The December 1941 surprise attack on Pearl Harbor did knock out the battle fleet, but it did not touch the aircraft carriers, which became the mainstay of the rebuilt fleet . </P>

How many aircraft carriers did the us have in ww2