Australia was a primary ally to the US during the Vietnam War.
South Vietnam was considered an ally of the US.
The Presidents who served during the Vietnam War are usually Eisenhower to Ford.
Approximately 2,594,000 US Servicemen served "in country" during the Vietnam War.
Simple, the US.
Prosecuted the war.
Over 58,000 US servicemen died in the Vietnam War.
Unwinnable.There was no country named Vietnam during the Vietnam War. The US didn't back down, it simply departed.
See Statistics about the Vietnam War.
US POWs still surviving in North Vietnam were released to the US in 1973; the vast majority of them were US Airmen who had been shot down during the air war over North Vietnam.