A defence treaty signed by Australia, New Zealand and the United States in 1951, the ANZUS Pact was prompted by the realisation during World War II that Australia and New Zealand could no longer rely solely on the United Kingdom in matters of national defence. The pact provides for mutual aid and cooperative action in the event of an armed attack on any of the member countries, their island protectorates, armed forces, aircraft or vessels in the Pacific.
Subsequent agreements between Australia and the United States based on the original ANZUS Pact have led to the establishment of the United States military and communications stations at North West Cape in Western Australia and Pine Gap in the Northern Territory.