When the fighting in Vietnam escalated the 1st Infantry Division was restructured and Battle groups were redesignated as infantry battalions. On 12 July 1965 the 1st and 2nd Battalions, 2nd Infantry were relieved from assignment to the 5th Infantry Division and assigned to the 1st Infantry Division with no change of station and in September 1965 the two battalions deployed to Vietnam, landing on the beach at Vũng Tàu in October 1965. From there they proceeded to their assigned areas, Phước Vĩnh for the 1st Battalion and Lai Khe for the 2nd Battalion. The battalions initially fought as light infantry in the areas north and west of Saigon. On 2 January 1967 the 2nd Battalion officially became a mechanized infantry battalion.