Huachuca because of its strategic border position. In 1913, the fort became the base for the "Buffalo Soldiers", the 10th Cavalry Regiment composed of African Americans. It served this purpose for twenty years. During General Pershing's failed Punitive Expedition of 1916–1917, he used the fort as a forward logistics and supply base. From 1916 to 1917, the base was commanded by Charles Young, the first African American to be promoted to colonel. He left for medical reasons. In 1933, the 25th Infantry Regiment replaced the 10th Cavalry at the fort. With the build-up during World War II, the fort had an area of , with quarters for 1,251 officers and 24,437 enlisted soldiers. The 92nd and 93rd Infantry Divisions, composed of African-American troops, trained at Huachuca. In 1947, the post was closed and turned over to the Arizona Game and Fish Department. However, at the outbreak of the Korean War, a January 1951 letter from the Secretary of the Air Force to the Governor of Arizona invoked the reversion clause of a 1949 deed. On 1 February 1951 the U.S. Air Force took official possession of Fort Huachuca, making it one of the few army installations to have had an existence as an air base. The army retook possession of the base a month later and reopened the post in May 1951 to train engineers in airfield construction as part of the Korean War build up. The engineers built today's Libby Army Airfield. On 1 May 1953, after the Korean War, the post was again placed on inactive status with only a caretaker detachment. On 1 February 1954, Huachuca was reactivated after a seven-month shut-down following the Korean War. It was the beginning of a new era for this one-time cavalry outpost, which saw Huachuca focused on electronic warfare. The army's Electronic Proving Ground opened in 1954, followed by the Army Security Agency Test and Evaluation Center in 1960, the Combat Surveillance and Target Acquisition Training Command in 1964, and the Electronic Warfare School in 1966. Also in 1966 the U.S. Army established the 1st Combat Support Training Brigade, whose mission was to train soldiers in the specialties of field wire and communication, telegraph communications (O5B wired and wireless), light tactical vehicle driving, wheeled vehicle maintenance, and food service and administration due to the expanding need for these skills in Vietnam. In 1967, Fort Huachuca became the headquarters of the