The 'Battle of Angaur' was fought between US and Japanese forces for possession of the island of Angaur in the Palau islands group (17 September/22 October 1944).

This battle was part of the larger 'Forager' strategic offensive campaign undertaken by the forces of Admiral Chester W. Nimitz’s Pacific Ocean Areas command between June and November 1944 in the Pacific theatre, and of 'Stalemate II' in particular.

Angaur is a very small limestone island, just 3 miles (4.8 km) long and separated from Peleliu by a 7-mile (11-km) strait, from which phosphate was mined. In the middle of 1944, the Japanese had 1,400 troops on the island under the overall command of Palau Sector Group's commander, Lieutenant General Sadae Inoue, and under the direct command of Major Ushio Goto, who was stationed on the island.  The weak nature of the Japanese defences in the Palau islands group and the potential for airfield construction made the islands attractive targets for the US forces after the 'Cataract' capture of the Marshall islands group, but a shortage of landing craft meant that operations against the Palau islands had to be postponed until the Mariana islands had been taken in 'Forager'.

Once the US assault on Peleliu was deemed well in hand, the 322^nd Regimental Combat Team was to land on the northern Beach Red, and the 321^st Regimental Combat Team on the eastern Beach Blue. Both these teams were component of Major General Paul J. Mueller’s 81^st Division.

The Japanese forces defending both Peleliu and Angaur island were the combat-hardened men of Lieutenant General Sadae Inoue’s 14^th Division with four years of experience fighting in Manchuria behind them, and personally sent to defend the Palau islands group by the Japanese prime minister General Hideki Tojo. The 1,400 men of the Angaur island garrison were the 1/59^th Regiment.

The US naval and aerial bombardment of Angaur by the battleship Tennessee, four cruisers and 40 Douglas SBD Dauntless single-engined dive-bombers of the aircraft carrier Wasp  began on 11 September 1944. Six days later, on 17 September, the two regimental combat teams landed on the north-eastern and south-eastern coasts. Lacking sufficient manpower strength to defend all the island’s possible landing) selected the beach which he believed would be most attractive to the US forces (called Beach Green by the Americans) for the construction of his beach defences. These comprised a formidable array of pillboxes, blockhouses, trenches and anti-tank ditches. As reconnaissance revealed the Japanese concentration against Beach Gree, Mueller opted to land his troops at the more physically constricted but less well-defended Beaches Red and Blue. The 322^nd Regimental Combat Team received sporadic mortar and machine gun fire but landed on Beach Red fairly unopposed and with light casualties. The landing of the 321^st Regimental Combat Team on Beach Blue faced heavier machine gun and mortar fire, but the team was able to get ashore with minimal casualties. Unknown to the US forces, Angaur was all part of the Japanese new defence-in-depth strategy that they and the 1^st Marine Division would also face on nearby Peleliu. This strategy was to now allow the Americans to land against only minimal opposition and start their move inland, only then to come up against the Japanese in-depth defensive lines. The Japanese concept also called for the start of massed nocturnal counterattacks while the bulk of the US forces was still heavily congested on the beach-heads, and thud drive the landed forces back into the sea. Suicidal banzai attacks, of the type seen on Tarawa, Guadalcanal and Saipan were now seen as counterproductive and were therefore forbidden. Both regimental combat teams were counterattacked during the night, but for the Japanese achieved little more than quickly depleting their valuable and irreplaceable troop numbers. Late the next day on 18 September, the two regimental combat teams were able to link on the island’s north-eastern quadrant and start the US teams' pushes to their respective objectives. By the end of 18 September, the US forces had taken the north-eastern third of the island and driven a long but narrow salient to the phosphate facility near the island’s western coast.

By the end of the third day, 19 September, the 81^st Division had cut the island in half with an advance from east to west. There were now two pockets of Japanese resistance: the main force was on Romauldo Hill in the island’s north-western quadrant, and the other dug in at the Beach Green defensive fortifications. After two days of harsh fighting and heavy casualties, the 321^st Regimental Combat Team had overrun the Beach Green defences and their 400 dug-in defenders by flanking them from behind. At a cost of 300 casualties, the southern half of the island was now declared secure. While the 321^st Regimental Combat Team was fighting in the island’s south, the 322^nd Regimental Combat Team moved across the island to the western coast, securing the only inhabited area of the island, named Saipan Town, and then swept to the north toward 'Shrine Hill' and Romauldo Hill, where the main 750-strong defence force was awaiting it in heavily dug-in positions in the island’s most formidable and difficult terrain. With the island’s southern half now secured, on 23 September the 321^st Regimental Combat Team was immediately despatched to nearby Peleliu, where the 1^st Marine Division was taking massive casualties and on the verge of becoming combat ineffective as a formation. Securing the rest of Angaur now fell to the 3,200 men of the 322^nd Regimental Combat Team.

The Japanese defensive network on Romauldo Hill and the intense fighting that would take place there was in effect, a microcosm of the brutal fighting taking place in the Umurbrogol pocket on Peleliu. The Japanese had honeycombed the entire hill with interconnecting caves, pillboxes and bunkers built into the coral rock, forming an almost impregnable position where the hardened defenders were dug in, determined to fight to the death and take as many US lives as possible with them. Near the top of the hill was a small bowl-like valley with a lake surrounded by coral ridges almost 100 ft (30 m) high, which became known as 'The Bowl'. To add to the defenders' advantage there was only one way into and out of 'The Bowl', through a narrow gorge, which the Americans later named 'Bloody Gulch'. As the 322^nd Regimental Combat Team advanced on 'The Bowl', near Lake Salome they were met with withering machine gun, mortar and sniper fire, and halted in its tracks.

From 20 September, the 322^nd Regimental Combat Team repeatedly attacked 'The Bowl', but the dug-in defenders repulsed each assault with artillery, mortars, grenades and machine guns, inflicting heavy losses. On a gradual basis, however, hunger, thirst, US artillery fire and US bombing took their toll on the Japanese, and by 25 September, after three costly frontal attacks, the US forces had penetrated 'The Bowl'. Rather than fight for possession of the caves, the Americans now used bulldozers to seal the entrances to caves and other possible Japanese lairs. By 30 September, the island was said to be secure, although the Japanese still had about 300 men in 'The Bowl' and surrounding areas, and these held out for almost four more weeks. Toward the end of the first week of October, the protracted conflict had degenerated into small-scale patrol actions in which each side used sniping, ambush and extensive booby-trapping. Goto, the island’s defence commander, was killed on 19 October fighting to keep possession of a cave. The last day of fighting was 22 October, after 36 days of fighting and blasting the Japanese resistance from their caves with explosives, tanks, artillery and flamethrowers. The 81^st Division had finally taken the whole of Angaur, although only at a high cost.

The 322^nd Regimental Combat Team had suffered 80% of the US casualties on Angaur, with a 47% casualty rate. On Peleliu, men of the 321^st and 323^rd Regimental Combat Teams continued in combat against the remaining 3,600 Japanese defenders holding out in the Umurbrogal pocket for almost two very sanguinary months, often resorting to fierce hand-to-hand combat. On Peleliu, another 282 men of the 81^st Division lost their lives, with another 4,409 wounded. Of all the casualties sustained by the 81^st Division in 'Stalemate II', only about 52% were ever again deemed sufficiently fit to return to duty. A great number of the US casualties were the result of head wounds inflicted by extremely accurate Japanese sniper fire and their use of smokeless powder.

The battle is one of the very few Pacific War engagements in which Allied casualties exceeded those of the Japanese, attesting to the ferocious Japanese resistance put up on the island.

Airfields were being under construction even as the battle was still being fought, but the delay in the start of the Palau islands operation meant that the airfields were not ready in time for the start of the 'King' operations in the Philippine islands group in October 1944. Admiral William F. Halsey, commander of the US 3^rd Fleet, had argued before the invasion of the Palau islands group that the operation was unnecessary, and military historians have generally agreed with him, suggesting that the main benefit was the combat experience gained by the 81^st Division.

During the fighting, 'Seabee' construction units created an airstrip that would house Consolidated B-24 Liberator four-engined heavy bombers of the 7^th Army Air Force’s 494^th Bombardment Group, which engaged in frequent bombings of the Philippine islands and others of the Palau islands group. 

The 81^st Division moved on directly to the battle on Peleliu to aid the 1^st Marine Division, which had encountered extremely stiff resistance in the central highland of that island. The division remained on Peleliu for another month, slowly taking the island and mopping-up the remaining Japanese forces.