With Mindoro island already in Allied hands since 16 December 1944 and the campaign for the recapture of Luzon already in full swing, the Americans wanted to establish another base of operations that would diminish the threat of Japanese troop incursions from the larger islands down south and cut off reinforcements coming from Japanese-occupied Indochina in mainland Asia via the South China Sea and the southwestern Sulu Sea.

The U.S. Eighth Army of Lt. Gen. Robert L. Eichelberger was directed to invade and seize the provincial capital of Palawan, Puerto Princesa, after which they would proceed to the Zamboanga Peninsula in western Mindanao and parts of the Sulu Archipelago.

[1] The primary objectives were to complete the isolation of the central Philippine islands of Panay, Negros, Cebu and Bohol and to expand the range of Allied air operations.

Farther inland, the coastal plain gave way to heavily forested mountains that offered great defensive potential to Japanese forces.

The men of the 186th RCT quickly fanned out, with two battalions striking north along the eastern side of Puerto Princesa Harbor while a third battalion crossed the bay at its midpoint and then pushed north, but then as the first day progressed, it became clear to the invading American troops that the Japanese troops—holdovers from Lt. Gen. Sōsaku Suzuki's 35th Army—would not put up a fight at Puerto Princesa and had withdrawn into the hills to the northwest.

The 186th RCT encountered little opposition until its third day ashore on 3 March when fierce fighting erupted as soldiers entered the hills that lay about 10 mi (16 km) north of the harbor.

Mopping up activities on Palawan lasted until late April, when the remaining Japanese simply withdrew farther into the trackless mountain jungles of Palawan—a pattern that repeated during all of the major operations in the southern Philippines—after which many were stalked and killed by U.S. troops and Filipino guerrillas.