<Ul> <Li> Soviet Union </Li> <Li> Cuba </Li> <Li> Czechoslovakia </Li> <Li> East Germany </Li> <Li> Poland </Li> </Ul> <Ul> <Li> Bulgaria </Li> <Li> Hungary </Li> <Li> Romania </Li> <Li> Sweden </Li> </Ul> <Ul> <Li> South Vietnam </Li> <Li> United States </Li> <Li> Kingdom of Cambodia (1967--1970) </Li> <Li> Khmer Republic </Li> <Li> Kingdom of Laos </Li> <Li> South Korea </Li> <Li> Thailand </Li> <Li> Australia </Li> <Li> Philippines </Li> <Li> New Zealand </Li> </Ul> <Li> Kingdom of Cambodia (1967--1970) </Li>

Where did most of the fighting occur in vietnam