This thesis is an analysis of the New Zealand Government's decision-making on combat military aid to South Vietnam and of subsequent decision-making on the admission of nuclear-powered ships to New Zealand ports. Particular emphasis is given to an explanation of the United States' influence on policy makers' definitions of the situations in order to give a greater understanding of New Zealand's continuing alliance relationship under ANZUS. The New Zealand Government characterised its own position on Vietnam in terms of certain dominant images which were influenced considerably by the United States. Furthermore, it is apparent that New Zealand's primary objective in Vietnam was not so much to win a war in South-East Asia as to secure itself against the possibility of reduced United States protection if it was not seen to be giving all-important symbolic support - particularly in the face of considerable Australian enthusiasm for a military contribution. With the post-Vietnam reduction of America's global involvement, New Zealand has continued to act with the feeling of constraint as an American client state, or rather, as a 'co-client' with one eye for Australia's actions.