<P> Naval doctrine had to be changed overnight . The United States Navy (like the IJN) had followed Alfred Thayer Mahan's 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 . </P> <P> 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 . </P> <P> By war's end in 1945, the United States Navy had added nearly 1,200 major combatant ships, including twenty - seven aircraft carriers and eight "fast" battleships, and ten prewar "old" battleships totaling over 70% of the world's total numbers and total tonnage of naval vessels of 1,000 tons or greater . </P> <P> On 16 June 1941, after negotiation with Churchill, Roosevelt ordered the United States occupation of Iceland to replace the British invasion forces . On 22 June 1941, the U.S. Navy sent Task Force 19 (TF 19) from Charleston, South Carolina, to assemble at Argentia, Newfoundland . TF 19 included 25 warships and the 1st Provisional Marine Brigade of 194 officers and 3714 men from San Diego, California under the command of Brigadier General John Marston . Task Force 19 (TF 19) sailed from Argentia on 1 July . On 7 July, Britain persuaded the Althing to approve an American occupation force under a U.S.--Icelandic defense agreement, and TF 19 anchored off Reykjavík that evening . U.S. Marines commenced landing on 8 July, and disembarkation was completed on 12 July . On 6 August, the U.S. Navy established an air base at Reykjavík with the arrival of Patrol Squadron VP - 73 PBY Catalinas and VP - 74 PBM Mariners . U.S. Army personnel began arriving in Iceland in August, and the Marines had been transferred to the Pacific by March, 1942 . Up to 40,000 U.S. military personnel were stationed on the island, outnumbering adult Icelandic men (at the time, Iceland had a population of about 120,000). The agreement was for the U.S. military to remain until the end of the war (although the U.S. military presence in Iceland remained through 2006). </P>

How many aircraft carriers did the united states build during world war ii