Australia’s foreign policy has always been determined more by her relations with the great powers than by her relations with the middle and small states in her neighbourhood. It is by great powers, with one possible exception, that Australia has felt threatened, and to other great powers that she has chiefly looked for protection against them. In the years 1966–70 Australia’s foreign policy was dominated by the Vietnam war. In April 1965 Australia committed combat troops to Vietnam formally in response to a request from the government of the Republic of Vietnam, for assistance against what it claimed was aggression from North Vietnam. But what primarily accounted for this decision was the belief that Australia should support her great power ally, the United States, in the stand it was making against communist expansion in Asia, emanating from China and, to a lesser extent, the Soviet Union.