Beginning the offensive, United States Marine Corps and United States Army forces, with support from the United States Navy, executed landings on Saipan in June, 1944. In response, the Imperial Japanese Navy's combined fleet sortied to attack the U.S. Navy fleet supporting the landings. In the resulting aircraft carrierBattle of the Philippine Sea (the so-called “Great Marianas Turkey Shoot”) on 19–20 June, the Japanese naval forces were decisively defeated with heavy and irreplaceable losses to their carrier-borne and land-based aircraft. Only a few of the twenty-four thousand Japanese defenders on the island were captured; large numbers of local civilians threw themselves and their children off high cliffs rather than be captured.
Drawing of the Mariana and Palau Islands campaign
Thereafter, U.S. forces executed landings on Guam and Tinian in July, 1944. After heavy fighting, Saipan was secured in July and Guam and Tinian in August, 1944. The U.S. then constructed airfields on Saipan and Tinian where B-29s were based to conduct strategic bombing missions against the Japanese mainland until the end of World War II, including the nuclear attacks on Hiroshima and Nagasaki.
In the meantime, in order to secure the flank for U.S. forces preparing to attack Japanese forces in the Philippines, in September, 1944, U.S. Marine and Army forces landed on the islands of Peleliu and Angaur in Palau. After heavy and intense combat on Peleliu, the island was finally secured by U.S. forces in November, 1944.
Following their landings in the Mariana and Palau Islands, Allied forces continued their ultimately successful campaign against Japan by landing in the Philippines in October, 1944 and the Volcano and Ryukyu Islands beginning in January, 1945.