The battle was part of a larger offensive campaign known as Operation Forager, which ran from June to November 1944 in the Pacific Theater.

[10] However, after repeated Imperial Japanese Army defeats in previous island campaigns, Japan had developed new island-defense tactics and well-crafted fortifications, which allowed them to offer stiff resistance[11] and extended the battle to more than two months.

"[12] In the US, the battle was controversial because of the island's negligible strategic value and the high casualty rate incurred by American troops during the fighting, which exceeded that of all other amphibious operations during the Pacific War.

The strategy proposed by General Douglas MacArthur called for the recapture of the Philippines, followed by the capture of Okinawa, then an attack on the Japanese home islands.

Admiral Chester W. Nimitz favored a more direct strategy of bypassing the Philippines but seizing Okinawa and Taiwan as staging areas to an attack on the Japanese mainland, followed by the future invasion of Japan's southernmost islands.

U.S. President Franklin D. Roosevelt traveled to Pearl Harbor to personally meet both MacArthur and Nimitz and hear their arguments.

[17] After their losses in the Solomons, Gilberts, Marshalls and Marianas, the Imperial Japanese Army assembled a research team to develop new island-defense tactics.

Previously, Japanese island garrisons had heavily contested enemy landings on the beach itself, which rendered them highly vulnerable to naval bombardment.

These changes in tactics were designed to force the Americans into a war of attrition, compelling them to spend more troops, materiel and time to secure Japanese island garrisons.

Engineers added sliding armored steel doors with multiple openings to many cave entrances, providing extra protection and concealment for both artillery and machine guns.

The caves and bunkers were connected to a vast tunnel and trench system throughout central Peleliu, which allowed the Japanese to evacuate or reoccupy positions as needed, and to take advantage of shrinking interior lines.

The beaches were also filled with thousands of obstacles for the landing craft, principally mines and a large number of heavy artillery shells buried with the fuses exposed, designed to explode when they were run over.

Neither Nakagawa nor his superior officers expected the garrison to survive if Peleliu was attacked, and Japanese military planners made no contingencies to evacuate any survivors.

A Navy Underwater Demolition Team cleared the beaches of some obstacles, while warships began their pre-invasion bombardment of Peleliu on 12 September.

United States Pacific Fleet[23] Admiral Chester W. Nimitz US Third Fleet Admiral William F. Halsey Jr. Joint Expeditionary Force (Task Force 31) Vice Admiral Theodore S. Wilkinson Expeditionary Troops (Task Force 36) III Amphibious Corps[c] Major General Julian C. Smith,[d] USMC Western Landing Force (TG 36.1) Major General Roy S. Geiger, USMC 1st Marine Division Beach assignments Palau District Group[26] Lieutenant General Inoue Sadae[h] (HQ on Koror Island) Vice Admiral Yoshioka Ito Maj. Gen. Kenjiro Murai[i] 14th Division (Lt. Gen. Sadae) Peleliu Sector Unit (Lt. Col. Kunio Nakagawa[j]) US Marines began landing on Peleliu at 08:32 on 15 September.

[1]: 42–45  As the additional landing craft approached the beaches, the Marines on shore were caught in a crossfire when the Japanese opened the steel doors guarding their positions and began firing artillery.

The 7th Marines faced a cluttered Orange Beach 3, with natural and man-made obstacles forcing the LVTs to bunch together and approach in column.

Their biggest push in the south moved 1 mile (1.6 km) inland, but the 1st Marines to the north made very little progress in the face of extremely heavy Japanese resistance.

After capturing the airfield, they rapidly advanced to the eastern end of Peleliu, leaving the island's southern defenders to be destroyed by the 7th Marines.

The Corsairs began dive-bombing missions across Peleliu, firing rockets into open cave entrances in support of infantry attacks, and dropping napalm.

This was only the second time that napalm had been used in the Pacific theater, [citation needed] and it proved effective at burning away vegetation hiding spider holes, usually killing their occupants.

The grenade detonated the 47 mm's shells, forcing the Japanese defenders out with their bodies alight and their ammunition belts exploding around their waists.

By the time reinforcements arrived, the company had successfully repulsed all the Japanese attacks, but had been reduced to 18 men, suffering 157 casualties during the battle for The Point.

Captain Everett P. Pope and his company penetrated deep into the ridges, leading his remaining 90 men to seize what he thought was Hill 100.

[1]: 83  Col. Harris adopted siege tactics, using bulldozers and flamethrower tanks to methodically destroy Japanese positions, and pushed into the ridges from the north.

[1]: 81 The reduction of the Japanese positions in "the Pocket" around Umurbrogol mountain has been called the most difficult fight that the U.S. military encountered during the entire war.

[33] Naval bombardment prior to amphibious assault at Iwo Jima was only slightly more effective than at Peleliu, but at Okinawa the preliminary shelling was greatly improved.

[34] Frogmen performing underwater demolition at Iwo Jima confused the enemy by sweeping both coasts, but later alerted Japanese defenders to the exact assault beaches at Okinawa.

[34] American ground forces at Peleliu gained experience in assaulting heavily fortified positions, which they would encounter again on both Iwo Jima and Okinawa.

Halsey actually recommended that the landings on Peleliu and Angaur be canceled, too, and their Marines and soldiers be sent to Leyte Island instead, but this plan was overruled by Nimitz.