World War II: The War at Sea

The U.S. Navy grew into a formidable force in the years prior to World War II, with battleship production being 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.

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.

Naval doctrine had to be changed overnight. The United States Navy (like the IJN) had followed Alfred Thayer Mahan emphasis on concentrated groups of battleships as the main offensive naval weapons. The loss of the battleships at Pearl Harbor forced Admiral Ernest J. King, the head of the Navy, to place primary emphasis on the small number of aircraft carriers.

The U.S. Navy grew tremendously as the United States was faced with a two-front war on the seas. It achieved notable acclaim in the Pacific Theater, where it was instrumental to the Allies' successful "island hopping" campaign. The U.S. Navy fought six great battles with the Imperial Japanese Navy (IJN): the Attack on Pearl Harbor, Battle of the Coral Sea, the Battle of Midway, the Battle of the Philippine Sea, the Battle of Leyte Gulf, and the Battle of Okinawa.

By war's end in 1945, the United States Navy had added nearly 1,200 major combatant ships, including 27 aircraft carriers and 8 battleships, and had over 70% of the world's total numbers and total tonnage of naval vessels of 1,000 tons or greater.