MacArthur planned to prevent attacks in his rear area during the reconquest of the Philippines by taking the Morotais and the Palaus. The most heavily defended island in the Palaus was Peleliu. He felt that he need to hold Peleliu before he could move on the Philippines. Vice Admiral William Halsey argued against the operation, arguing that the Philippines were lightly defended. The Palaus, especially, were not required to take the Philippines, enough distance away to be isolated and left to die on the vine.
But MacArthur would not be dissuaded. On September 15, 1944, the first waves from the US 1st Marine Division landed to little opposition. When the first wave was already ashore, the mortars and machine guns sank twenty-four Higgins boats onshore or in the second wave within minutes. MacArthur's planners had failed to make adequate reconnaissance of the island. The only maps were from 1923, and they neglected to show the dense jungle or the caves on the island.