The Vietnam War is often regarded as a low point for the U.S. Army due to the use of drafted personnel, the unpopularity of the war with the American public, and frustrating restrictions placed on the military by American political leaders. While American forces had been stationed in the Republic of Vietnam since 1959, in intelligence & advising/training roles, they were not deployed in large numbers until 1965, after the Gulf of Tonkin Incident. American forces effectively established and maintained control of the "traditional" battlefield, however they struggled to counter the guerrilla hit and run tactics of the communist Viet Cong and the North Vietnamese Army. On a tactical level, American soldiers (and the U.S. military as a whole) did not lose a sizable battle.^[22]

A U.S. Army infantry patrol moves up to assault the last North Vietnamese Army position at Dak To, South Vietnam during Operation Hawthorne

During the 1960s the Department of Defense continued to scrutinize the reserve forces and to question the number of divisions and brigades as well as the redundancy of maintaining two reserve components, the Army National Guard and the Army Reserve.^[23] In 1967 Secretary of Defense Robert McNamara decided that 15 combat divisions in the Army National Guard were unnecessary and cut the number to 8 divisions (1 mechanized infantry, 2 armored, and 5 infantry), but increased the number of brigades from 7 to 18 (1 airborne, 1 armored, 2 mechanized infantry, and 14 infantry). The loss of the divisions did not set well with the states. Their objections included the inadequate maneuver element mix for those that remained and the end to the practice of rotating divisional commands among the states that supported them. Under the proposal, the remaining division commanders were to reside in the state of the division base. No reduction, however, in total Army National Guard strength was to take place, which convinced the governors to accept the plan. The states reorganized their forces accordingly between 1 December 1967 and 1 May 1968.