The 4th Infantry Division deployed from Fort Lewis to Camp Holloway, Pleiku, Vietnam on 25 September 1966 and served more than four years, returning to Fort Carson, Colorado on 8 December 1970. Two brigades operated in the Central Highlands/II Corps Zone, but its 3rd Brigade, including the division's armor battalion, was sent to Tay Ninh Province northwest of Saigon to take part in Operation Attleboro (September to November 1966), and later Operation Junction City (February to May 1967), both in War Zone C. After nearly a year of combat, the 3rd Brigade's battalions officially became part of the 25th Infantry Division in exchange for the battalions of the 25th's 3rd Brigade.