Because they (Cambodian and Vietnamese) are Happily Married !
Re-education, or brainwashing.
Cambodia was neutral.
They were neutral.
Cambodia was being invaded by both American and japenesse troops during their battles.
Who told you it was, specifically how was Cambodia involved in the war? If you can boil down specifics, then maybe an explanation can be given.
Richard M. Nixon introduced the policy of Vietnamization in his speech on November 3, 1969.
The policy of US withdrawal and "Vietnamization" spelled disaster for South Vietnam.Of course, the Republic of South Viet Nam should be the immediate answer. Certainly other countries in the region were impacted as well. Thailand, Laos and Cambodia all changed, as did China, who went to war with the newly formed government of Vietnam and Cambodia.
nixon
July 1969
Nixon
The Vietnamization plan involved the gradual withdrawal of U.S. troops from Vietnam while increasing the combat role of South Vietnamese forces, thus shifting responsibility for the war onto them. It also included efforts to prepare South Vietnam for self-sufficiency in defending itself against communist aggression.
Re-education, or brainwashing.