The 25th Marines was activated on 1 May 1943, at Marine Corps Base Camp Lejeune, North Carolina and was initially composed of Marines from throughout the Northeast. The regiment was subsequently assigned to the 4th Marine Division for service in World War II. Initially located at Marine Corps Base Camp Pendleton, California, the regiment was ordered to the Pacific Theater in January 1944 and participated in the Battle of Kwajalein, Saipan, Battle of Tinian and the Battle of Iwo Jima.