The US asked them to.
One regiment of Centurion medium tanks, Infantry, Artillery, and some aviation assets.
All three Australian armed forces and civilian formations were involved in the Vietnam war from 1962 to 1972. The related link lists them.
On 28 April, 1965, Australian Prime Minister, Robert Menzies, announced that Australian troops would be sent to support the United States forces in the Vietnam war. The first Australian troops arrived in Vietnam in May 1965.
Australians arrived in Vietnam during the early 1960's along with US Advisery Forces; Australian Buildup of Australian Regulars appeared on line with US Forces in 1965. Over 50,000 Australian Servicemen fought in Vietnam, and approximately 63,700 Australian Men had been drafted into service. About 19,000 Australian Draftees served "in country" in Vietnam, and nearly 600 of them died there. Most Aircraft, Riverine Craft, Trucks, and Artillery were US designed or of US origin in the Australian Service. Australian Forces wore US Steel Helmets (when they wore them at all) but carried FN FAL (Belgium Made) rifles & used British Manufactured or Designed CENTURIAN TANKS in the Vietnam War. Australian tank crewmen operated about 58 Centurian's in country. The Australian Mechanized Infantrymen used US M-113 APC's (Armored Personnel Carriers). Australia re-deployed from the war, on line with US Forces in 1972/1973.
Yes it did, you might be surprised to know that Australian forces were fighting in Vietnam 3 years before America even joined the war. Aussies were also the first to follow the Viet Kong into the tunnels. Australias contribution was modest with thousands deployed at any one time. The most famous battle of the war involving Australia was the Battle of Long Tan where 30 Aussies fought off 2000+ Viet Kong. It is a shame that the war was lost in the end.
Over 3,000 Australian Servicemen wounded in Vietnam.
Australian maintained a troop level of approximately 8,000 men in Vietnam during the war.
The Australian government experienced anti-war demonstrations.
Over 50,000 Australian Servicemen fought in the Vietnam War.
Australia sent 4 Navy Destroyers and a regiment of Australian Centurion tanks into the Vietnam War.
The forces of the Republic of South Vietnam.