The Battle of Peleliu, codenamed Operation Stalemate II by the US military, was fought between the United States and Japan during the Mariana and Palau Islands campaign of World War II, from 15 September to 27 November 1944, on the island of Peleliu.

The Mariana and Palau Islands campaign, also known as Campaign Plan Granite II, was an offensive launched by United States forces against Imperial Japanese forces in the Pacific Ocean between June and November 1944 during the Pacific War. The campaign consisted of Operation Forager, which captured the Mariana Islands, and Operation Statemate, which captured Palau. Operation Causeway, the invasion of Taiwan was also planned but not executed. The offensive, under the overall command of Chester W. Nimitz, followed the Gilbert and Marshall Islands campaign and was intended to neutralize Japanese bases in the central Pacific, support the Allied drive to retake the Philippines, and provide bases for a strategic bombing campaign against Japan.