This is the first of a series of volumes prepared in the Historical Branch, Department of Internal Affairs, dealing with New Zealand's involvement in conflicts since the Second World War. It covers the political, diplomatic, and social aspects of New Zealand's involvement in the Korean War, and seeks to explain why New Zealand felt the need, for the fourth time in its history, to send soldiers overseas to fight in a conflict whose direct significance to New Zealand's security was not immediately obvious. Although New Zealand's contribution to the United Nations forces was not large, the crisis had a major impact in New Zealand eyes to confirm the necessity of firmly resisting apparent Soviet encroachment. They also provided an opportunity for New Zealand to pursue its goal of obtaining a commitment by the United States to its security. The Anzus Treaty of 1951 was the successful achievement of this objective, and was to have a far-reaching impact on New Zealand's international relations in the long term.