Two days after the 13th AAF's last run over Palau, carrier elements of Task Force 38, the invasion force for Operation Stalemate II, began a series of strafing and bombing runs on 6-8 September over key military sites. During the prior three months, the plans for the invasion of Palau had undergone substantial modification. Admiral Bull Halsey, Commander of the Third Fleet, wanted to skip Palau completely, but Admiral Nimitz overruled him.
The original plan called for a two-pronged invasion, one in the south concentrating on the capture the airfield on Peleliu, and one to the north on Babeldaob. But ongoing military intelligence cast serious doubt on attacking Babeldaob: of 35,000 troops stationed in Palau, 25,000 were thought to be on Babeldaob in powerfully fortified and upgraded positions and there were no beaches to support a large amphibian landing. The new plan proposed the taking only of Peleliu and its nearby neighbor, Angaur. Once captured, airfields on both of these islands could be used or developed to support air suppression of the larger northern Japanese garrison on Babeldaob. Since no significant Japanese shipping remained and U. S. mines blocked all naval routes, this new plan, theoretically, met the combined needs of protecting the Philippine flank while minimizing American losses.
The task of capturing Peleliu fell to the First Marine Division (of Guadalcanal fame). On 15 September, after three days of constant bombardment of Peleliu by American battleships and carrier-based aircraft (the only US naval loss occurred the day before, with the sinking of the USS Perry by a sea mine off of Angaur), the Marines landed on Peleliu beaches . Enemy contact was immediate, intense, and bloody - but surprisingly devoid of banzai charges at the beachhead. More surprises lay ahead.
Prior to the invasion, Lt. Gen. Inoue had been given instructions from Japan to hold and/or delay the enemy at all costs. The Japanese had learned from Guadalcanal and Tarawa the utter futility of massed suicide charges, so general Inoue had imported conscripted Korean laborers to dig hundreds of caves, some very extensive, into the coral limestone ridges. These caves proved impervious to U. S. naval gunfire and air attacks. The Japanese on Peleliu, under the command of Col. Nakagawa Kunio, planned to make their stand from these caves, fighting a battle of attrition they knew they could not win. When the naval and air bombardment failed to penetrate these caves, the Marines were forced to come to the Japanese. This strategy of entrenchment was heavily used for the remainder of the war, later memorialized at Iwo Jima and Okinawa, but first proven on Peleliu. American losses were heavy from the beginning and would remain so throughout the battle.
As early as 18 September, American aircraft began landing on the captured Peleliu airfield. Six days later, the first Marine fighter units of Marine Air Group (MAG) 11 landed there, freeing carrier forces from further air support over Palau. With the ongoing ground battle only yards away, fighters from Marine Fighter Squadron (VMF) 541(N), 114, 122 and 121 landed on Peleliu. On 17 September, two regimental combat teams of the U. S. Army's 81st Infantry landed on Angaur, effectively neutralizing Japanese forces there within three days.
While still under enemy fire, the 1884th Engineer Aviation Battalion began construction of a 6500-foot runway on Angaur for receiving B-24 units of the 7th AAF. Taking the less-fortified Angaur went as planned, but the Peleliu invasion did not. Projected to take only four days to complete, Peleliu turned into a prolonged bloodbath for both sides, not to officially cease until 27 November. STALEMATE II turned out to be an apt name for this operation: total American casualties for this virtually forgotten battle amounted to 8,583 with 1,285 killed in action, to be eclipsed in the Pacific only by those casualties from Iwo Jima and Okinawa.
An estimated 11,000 Japanese were killed on Peleliu, most in fierce cave-by-cave fighting. VMF 114, 122 and 121 were Corsair fighter-bomber units. Trained both to fight in air-to-air combat and to provide ground support, most of these Corsair aviators stayed on Peleliu for the duration. Their immediate mission began less than 500 yards from take-off, making the shortest bombing runs in all of World War II. They also covered Babeldaob and Koror, but AA batteries knocked a lot of Corsairs out of the skies. In spite of these losses, the daily Marine flights did prevent the Japanese from counterattacking Peleliu and Angaur. By November the 7th AAF also began missions from Angaur to Babeldaob and Koror. It must have seemed strange to crews, used to long distant raids, to go from take-off to landing in less than an hour. And such was the nature of war that, although these Army and Marine air units were only six miles apart and flew missions against the same targets, the crews were barely aware of each other.