In the years preceding the Vietnam War, there were many close calls with insurgent communism dating right back to World War 2.
All of these plus others contributed to the Australian belief that we join the Vietnam War.
South Vietnam, Cambodia and Laos were also guaranteed protection.
The other main alliance that Australia had that helped in security was the ANZUS Agreement signed in 1951.
The American presence in South Vietnam was seen as an extension of the principle of containment.
That principle had it that in the interests of avoiding a global war no great attempt would be made to liberate countries, which had fallen to communism, but the spread of communism, inevitably by dictatorial means, would be resisted.The official reason of Australia's decision to enter the Vietnam War holds that Australia, at the request of the South Vietnamese government, and together with the noble American nation entered (reluctantly) into war, to safeguard the world from communist peril.The geopolitical case for our commitment was equally simple.It was an intense 12-year jungle war fought by the British, British Commonwealth and Malay forces against the guerrillas of the Malayan Communist Party (MCP) led by Communist fanatic Chin Peng.Australia contributed troops in 1950, to help the British in preventing Malaya becoming a communist state of China.This formalised the relationship between Australia, America and New Zealand and one would come to the other's aid in the event of attack.The Malayan Emergency (1948-60) was the only war the West won against insurgent communism.When Menzies made his statement suggesting, "The takeover of South Vietnam would be a direct military threat to Australia," the anti-Communist convictions developed over the previous five years were now convincing them to intervene and this action led Australia into the "dilemma of the Vietnamese civil war."Communism was seen as an aggressive force to destroy the western society of capitalism and democracy.In 1945, there was one Communist state in the world, Russia by 1949 with the establishment of the Communist Peoples' Republic of China led by Chairman Mao, 11 countries were now communists.For many Australians who had lived through World War 2, there was greater fear because they could see the parallels between the imminent threats of invasion through communism with the threat that the Japanese had produced 20 years earlier.The same sort of pattern could be seen with the domino effect, how they were slowly jumping from country to country gaining more power and Australia would be at threat if action weren't taken.