New Zealand's alignment and participation in the Cold War was determined by the decision of the 1940s Labour government to back the United States and Great Britain (that concord was crucial) in their disagreements with the Soviet Union. The decision was questioned, though not overturned, by the Left, with communists and others claiming that Labour had rejected both peace and socialism.
As the United States escalated its military involvement, New Zealand and other American allies came under increased pressure to provide combat assistance. An unenthusiastic Holyoake responded to American entreaties in December 1964 by pointing to New Zealand's commitments in Malaysia, where its forces were involved in Confrontation. American plans to introduce ground combat forces (as opposed to the combat advisers previously deployed) were not favoured in Wellington, New Zealand again diverging from the more 'robust' approach taken by Australia.
New Zealand added several other small units and groups of personnel, including members of both the RNZN and RNZAF, to its commitment in Vietnam during the period 1967 to 1969. The 1st New Zealand Services Medical Team was deployed in April 1967 with the role of providing medical and surgical assistance to South Vietnamese civilians and encouraging the development of indigenous capacity in this field.
Twenty-seven strong at its peak, it operated initially at Qui Nonh before moving north to Bong Son. In July 1967 an RNZAF pilot was made available to 9 Squadron RAAF, which operated Iroquois helicopters, and two more were provided in 1968. From December 1968 two forward air controllers served with the 7th US Air Force. The RNZAF also made a more general contribution, insofar as its transport aircraft supported the commitment in Vietnam throughout New Zealand's involvement. In January 1969 a 26-man Special Air Services troop arrived in Vietnam, raising the strength of New Zealand's force to its peak of 543 men. It was involved in intelligence gathering operations in Phuoc Tuy province, mounting 155 patrols in all.
New Zealand's limited military involvement in the Vietnam War was overshadowed by the wide-ranging debate about the conflict which erupted at home following the rise from the mid 1960s of an organised anti-Vietnam War movement.
It is difficult to assess which side had the better of this debate during the Vietnam War. The decision to send combat forces to Vietnam initially appeared to enjoy high levels of public support, and the National Party did not suffer unduly adverse electoral consequences, being returned to office twice - in 1966 and 1969 - during the Vietnam period. Nor was the government ever sufficiently concerned by domestic criticism to change a policy it had adopted largely for alliance reasons.