“The bitterest battle of the war for the Marines”.
The Battle of Peleliu, codenamed Operation Stalemate II, was fought from September–November 1944 on the island of Peleliu, present-day Palau. U.S. Marines of the First Marine Division and later soldiers of the U.S. Army’s 81st Infantry Division, fought to capture an airstrip on the small coral island. This battle was part of a larger offensive campaign known as Operation Forager which ran from June 1944 to November 1944 in the Pacific Theater of Operations.
Major General William Rupertus, USMC—commander of 1st Marine Division—predicted the island would be secured within four days. However, due to Japan’s well-crafted fortifications and stiff resistance, the battle lasted over two months. In the United States, it was a controversial battle because of the island’s questionable strategic value and the high casualty rate, which was the highest for U.S. military personnel of any battle in the Pacific War (font Wikipedia).