Operation Forager was the combined Allied operation in the Marianas and Palau from June to November 1944. The operation included various battles at Saipan, Guam and Peleliu. It was an operation primarily targeting the seizure of new airfields for further air campaigns over the Japanese home islands and the Philippines.
The campaign began on June 15 when the first U.S. Marines landed ashore Saipan. The 2nd and 4th Marine division landed on the beaches to defeat the Japanese garrison stationed there. Up to 8,000 Marines soon flooded onto the beaches. During the landings, a gap emerged between the two Marine divisions; but they still secured a beachhead from which to press further inland.
To defeat the Marine landings at Saipan, the IJN (Imperial Japanese Navy) sent a fleet of three aircraft carriers, and further six light carriers, to intercept Task Force 58. They carried hundreds of carrier planes that thousands of land-based aircraft in the region reinforced. However, U.S. planes devastated the airfields in the Marianas before their arrival.
U.S. aircraft wiped the IJN First Air Fleet from the skies during the Battle of the Philippine Sea. Their submarines also intercepted, and sank, two of the Japanese carriers. U.S. aircraft intercepted the third IJN fleet aircraft carrier before they withdrew.
The Battle of the Philippine Sea secured the U.S. Marines' supply line in Saipan. Thereafter, they proceeded to advance northwards up the mountains of Saipan. When they secured Mount Tapochau, they cleared out the last pockets of Japanese troops in the north. The Battle of Saipan was largely over by July 9.
Having won the Battle of Saipan, the Marines landed in Guam on June 21 and Tinian on June 24. After securing beachheads, they advanced in both Tinian and Guam. The first to fall was Tinian, whilst a series of Japanese counter-attacks slowed the Marines in Guam. The U.S. Marines defeated the Japanese garrison by August 10.
The first stage of Operation Forager ended with the Marines occupying the Marianas. The second phase required further Marine landings in Palau. The primary Palau island to capture in this operation was Peleliu. To take Peleliu, the USA sent 17,500 Marines; but that was hardly a sufficient number in a battle that would last longer than expected. They landed in Peleliu on September 15.
The Japanese placed a battalion of defenders along the perimeter of Peleliu with bunkers supported by heavy machine guns and artillery. The Umurbrogol mountain also provided them with further advantages, and it was here that the Japanese army stationed most troops with a well concealed and fortified mountain fortress.
Before the Marines landed in September, the U.S. Navy and U.S. aircraft bombarded Peleliu. However, this preliminary bombardment was in fact somewhat ineffective. The Japanese garrisons remained firmly intact, so when the Marines began to land they did not make great progress on the beaches.
Elsewhere, the 5th Marine Regiment advanced more quickly. They were able to secure the airfield at Peleliu. As such, with the airfield taken U.S. planes began to provide greater air support for the marines on the ground. Corsair dive-bombers began bombing Japanese dugouts to further clear the ground of enemy troops.
Defeating the Japanese troops at Umurbrogol Mountain would take weeks. During this period an American infantry division provided further reinforcements for the Marines. Only by November 27 had the Americans effectively won the battle.
Operation Forager ended in triumph for the Allies. They had taken Saipan, Guam, Tinian, Peleliu and wiped out much of the IJN First Air Fleet. The U.S. Marines and Army secured a number of new airfields in the Marianas and Palau from which to provide air support for further campaigns in the Japanese home islands and Philippines.
With the battle over the Allies maintained their advance towards the Philippines. Although the airfields at Peleliu were by no means essential for the Philippines Campaign. About 1,794 Americans were lost in the Battle of Peleliu. Months later MacArthur and thousands of U.S. Marines landed at Luzon to retake the Philippines.