Since the partition of Vietnam in 1954 the Communist North had attempted to unite the country as a Communist state, fuelling US concern over the possible spread of Communism in SE Asia. After two US destroyers were reportedly fired on in the Gulf of Tonkin in 1964, a US army was sent to Vietnam, supported by contingents from South Korea, Australia, New Zealand, and Thailand, while American aircraft bombed North Vietnamese forces and areas of Cambodia. The Tet Offensive of 1968 damaged US confidence and US forces began to be withdrawn, finally leaving in 1973. The North Vietnamese captured the southern capital Saigon to end the war in 1975.