After an assignment as province senior adviser, Vann was made Deputy for Civil Operations and Revolutionary Development Support (CORDS) in the Third Corps Tactical Zone of Vietnam, which consisted of the twelve provinces north and west of Saigon—the part of South Vietnam most important to the US. CORDS was an integrated group that consisted of USAID, U.S. Information Service, Central Intelligence Agency and State Department along with U.S. Army personnel to provide needed manpower. Among other undertakings, CORDS was responsible for the Phoenix Program, which involved neutralization of the Viet Cong infrastructure.