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 Americans 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 twenty-seven aircraft carriers, 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.