The battalion was first activated on 1 May 1943, at Marine Corps Base Camp Lejeune, North Carolina, as the 2nd Battalion, 25th Marines. It was relocated during August–September 1943 to Camp Pendleton, California. In September 1943, 2/25 was assigned to the 4th Marine Division. The battalion was deployed to combat during January 1944 to Kwajalein Atoll, Marshall Islands. It participated in the following World War II campaigns: Kwajalein, Saipan, Tinian and Iwo Jima while under the command of Lieutenant Colonel Lewis C. Hudson. In October 1945, it relocated to Camp Pendleton, California and was deactivated on 31 October 1945.