The I Marine Amphibious Corps, or I MAC, was a formation of the United States Marine Corps. It was created on 1 October 1942, with most of the staff transferred from Amphibious Corps, Pacific Fleet (ACPF). It was then deployed to the South Pacific Areaa U.S.-led multinational military command active during World War II that was a part of the U.S. Pacific Ocean Areasfirst to Hawaii, then to New Caledonia. Consisting of the 3rd Marine Division, the 37th Infantry Division of the United States Army, and a brigade of the 3rd New Zealand Division, it conducted the invasion of Bougainville.