After the Second World War the United States, along with their French and British allies, frequently tested nuclear weapons in the Pacific region. In the 1950s New Zealand military personnel observed British and American nuclear tests in Australia, the Pacific and in Nevada, and vessels of the Royal New Zealand Navy were weather ships for British tests in the Indian Ocean. In 1963 the British, American and Soviet governments agreed to ban atmospheric tests. New Zealand also signed this treaty. Noticeable exceptions among the signatories were India, China and France.
New Zealand was involved in ongoing protest over French nuclear testing from the mid-1960s when France began testing nuclear weapons in French Polynesia. Mururoa (also called Moruroa) Atoll became the focal point for both the tests and opposition to them. Greenpeace vessels sailed into the test site in 1972, and the following year the New Zealand and Australian governments took France to the International Court of Justice in an attempt to ban tests. France ignored the court's ruling that they cease testing.
The third Labour government, led by Norman Kirk, responded by sending two navy frigates, HMNZS Canterbury and Otago, into the test area. A Cabinet minister was also selected to accompany this protest. Prime Minister Kirk put all the Cabinet ministers' names into a hat and drew out the name of Fraser Colman, the minister of immigration and mines. He sailed from Auckland on 25 June aboard the Otago, which carried a crew of 242. A month later the ship was at Mururoa, and those on board witnessed the first atmospheric test. Fraser Colman transferred to the Canterbury when it arrived to relieve the Otago on 25 July, and he and the crew of the Canterbury saw the second French atmospheric test on Mururoa. These protests achieved some limited success because in 1974 the new French president, Valéry Giscard d'Estaing, ordered that the tests move underground. With testing continuing, however, Mururoa remained a focus of anti-nuclear protest.