1^ST Battalion 12^th Marines came in to existence during the second World War.  The Battalion was activated 1 September 1942, at San Diego, California as the 4^th Battalion 12^th Marines and assigned to the 3d Marine Division.

         During October 1942 the Battalion relocated to Camp Dunlap, California.  Deploying to Auckland, New Zealand during March of 1943 only to be redeployed during July 1943 to Guadal Canal.  During this period the Battalion was heavily involved in numerous campaigns to include Bougainville, Guam and Iwo Jima.

After being re-designated on 5 April 1945 as 1^st Battalion 12^th Marines the Battalion was relocated during December 1945 to Camp Pendleton, California, only to be deactivated on 8 January 1946.

         Five years later the Battalion was reactivated on 20 June 1951 at Camp Pendleton, California and was assigned to the 3d Marine Division.  August 1953 1^st Battalion 12^th Marines deployed to Camp Mcnair, Japan and redeployed to South Camp Fuji, Japan during March 1956.

During March and April of 1965 the Battalion was called upon to deploy to the Republic of Vietnam.  The Battalion participated in the Vietnam war from April 1965 to September 1969 operating from Phu Bai, Da Nang, Cam Lo, Khe Sanh and Camp Carroll.  The Battalion after the Vietnam war was reduced to cadre status.

         During October 1969 the Battalion was reestablished at Camp Pendleton California and assigned to the 5th Marine Division.  One year later in November 1969 the Battalion was reassigned to the 5th Marine Expeditionary Brigade.

In April of 1971 the Battalion was reassigned to the 1^st Marine Division.  The Battalion deployed in June 1971 to Kaneohe Bay, Hawaii and was later reassigned to the 1^st Marine Brigade.  During the 1970’s and 1980’s the unit endured numerous training exercises to stay combat ready.

         1^st Marine Brigade re-designated 30 August 1985 as the 1^st Marine Amphibious Brigade.  In the years that followed 1^st Marine Amphibious Brigade re-designated as the 1^st Marine Expeditionary  Brigade.  

         1^st Battalion 12^th Marines participated in Operations Desert Shield and Desert Storm in Southwest Asia during September 1990 to April 1991.  In September 1994 the Battalion was reassigned to 3rd Marine Division as part of the III Marine Expeditionary Forces Hawaii.

          Elements of 1st Battalion, 12th Marines participated in Operation Iraqi Freedom during August 2004 to February 2005 and March 2005 to February 2006.

          From March to October 2007, 1st Battalion, 12th Marines participated in Operation Iraqi Freedom (OIF) 06-08.1. A year later, in September 2008, the Battalion redeployed to Al Anbar Province for OIF 08.2 until May 2009. Both times, 1/12 was reorganized as Task Force Military Police (TFMP) responsible for Convoy Security, Detainee Operations, Military Working Dogs and Point of Entry Security.