The 1st Marine Division (1st MARDIV) is a Marine division of the United States Marine Corps headquartered at Marine Corps Base Camp Pendleton, California. It is the ground combat element of the I Marine Expeditionary Force (I MEF). It is the oldest and largest active duty division in the United States Marine Corps, representing a combat-ready force of more than 19,000 personnel. It is one of three active duty divisions in the Marine Corps today and is a multi-role, expeditionary ground combat force. It is nicknamed "The Old Breed". Mission The division is employed as the ground combat element (GCE) of the I Marine Expeditionary Force or may provide task-organized forces for assault operations and such operations as may be directed. The 1st Marine Division must be able to provide the ground amphibious forcible entry capability to the naval expeditionary force (NEF) and to conduct subsequent land operations in any operational environment. Organization The 1st Marine Division currently comprises a headquarters battalion, four regiments and five separate battalions as follows: Headquarters Battalion 1st Marine Regiment 5th Marine Regiment 7th Marine Regiment 11th Marine Regiment 1st Reconnaissance Battalion 1st Light Armored Reconnaissance Battalion 3rd Light Armored Reconnaissance Battalion 1st Combat Engineer Battalion 3rd Assault Amphibian Battalion History Inter-War Years The lineal forebear of the 1st Marine Division is the 1st Advance Base Brigade, which was activated on 23 December 1913 at Philadelphia, Pennsylvania. (Subsequently, the brigade was redesignated on 1 April 1914, as the 1st Brigade, and on 16 September 1935, as the 1st Marine Brigade). The brigade consisted of the Fixed Defense Regiment and the Mobile Defense Regiment, later designated as the 1st and 2nd Regiments, 1st Brigade, respectively. In 1916, while deployed in Haiti, the two regiments were again redesignated, exchanging numerals, to then become the 2nd and 1st Regiments, 1st Brigade. Between April 1914 and August 1934, elements of the 1st Brigade participated in operations in Mexico, Haiti, the Dominican Republic, and Cuba, receiving campaign credit for service in each nation. While the 1st Brigade did not serve ashore in the European theater during the First World War, the brigade was awarded the World War I Victory Medal Streamer, with one bronze star, in recognition of the brigade's service during that conflict. On 16 September 1935, the brigade was redesignated as the 1st Marine Brigade and deployed to Guantanamo Bay, Cuba in October 1940. World War II The