Bombardment of Angaur by the battleship Tennessee, four cruisers, and 40 Douglas SBD Dauntless dive bombers from the aircraft carrier Wasp began on 11 September 1944.

After two days of harsh fighting and heavy casualties, the 321st had overrun the Green Beach defenses and the 400 dug in soldiers by flanking them from behind.

With the southern half of the island secured, on 23 September the 321st RCT was dispatched to nearby Peleliu, where the 1st Marine Division was taking massive casualties and nearing becoming combat ineffective as a unit.

The entire hill was honeycombed with interconnecting caves, pillboxes and bunkers built into the coral rock, forming an almost impregnable position where the defenders were dug in, determined to fight to the death and take as many American lives with them.

Near the top of the hill was a small bowl-like valley with a lake surrounded by ridges almost 100 feet (30 m) tall, which became known as "the Bowl".

From 20 September, the 322nd RCT repeatedly attacked the Bowl, but the dug in defenders repulsed them with artillery, mortars, grenades and machine guns, inflicting heavy losses.

[6] Toward the end of the first week of October, the protracted conflict had degenerated into patrol action with sniping, ambushing, and extensive booby-trapping employed by both sides.

A great number of American casualties were the result of head wounds inflicted by accurate Japanese sniper fire and their use of smokeless powder.

Admiral William F. Halsey, Jr. had argued before the invasion of the Palaus that the operation was unnecessary, and military historians have agreed with him, suggesting that the main benefit was the combat experience gained by the 81st Infantry Division.

During the fighting, Seabees created an airstrip that would house B-24 Liberator bombers of the 494th Bombardment Group, 7th Air Force which engaged in frequent bombings of the Philippines and other Palau Islands.