The Mariana and Palau Islands campaign, also known as Operation Forager, was an offensive launched by United States forces against Imperial Japanese forces in the Mariana Islands and Palau in the Pacific Ocean between June and November, 1944 during the Pacific War. The United States offensive, under the overall command of Chester Nimitz, followed the Gilbert and Marshall Islands campaign and was intended to neutralize Japanese bases in the central Pacific, support the Allied drive to retake the Philippines, and provide bases for a strategic bombing campaign against Japan.
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 carrier Battle 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.
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.