American island-hopping tactics through the Central Pacific proceeded with an attack on the Marianas in the north. Here the U.S. objectives were Guam and Saipan. Following an air and sea pounding, Saipan was invaded by 20,000 U.S. Marines on June 15, 1944. Altogether, the Americans landed 125,000 troops, compared to the 32,000 Japanese on the island. By June 18, the Japanese forces were split in half. News of the disaster at Saipan moved Japanese strategists in Tokyo to order the destruction of the U.S. fleet supporting the Saipan assault. On June 19, 1944, a mobile Japanese task force moved to engage the U.S. ships between the Philippines and the Marianas. The result was the Battle of the Philippine Sea, the biggest carrier engagement of the war. U.S. submarines sank two Japanese carriers, torpedo aircraft accounted for another carrier, and U.S. planes destroyed more than 350 Japanese aircraft.