Hey, something that I cant understand is 2 things.
(Time from 1975, Place: Cambodia, Vietnam).
First, why even Khmer Rouge attacked vietnam if they both communist and didnt was in war against each other before?
Second, both vietnam and cambodia where communists so why US picked side and supported cambodia?
By the way something I cant find, cambodia has a king now but the govermant is communist(like China, vietnam etc...) or no?
Thanks in advance.
First, there are a couple factors.
In the ancient times, the Cambodian empire was broken apart. Much of the ancient Cambodia land is now part of Vietnam, Laos, and Thailand. Khmer Rouge's goal is to turn their country back to medieval Cambodia Empire, and they want their ancient land back.
During the Vietnam War, the North Vietnamese used Cambodia and Laos as a route to transport troops and supplies, this led to U.S. bombing the hell out of those two countries.
After the Vietnam War, Vietnam emerged as the strongest nation in Indochina (Vietnam, Laos, Cambodia). Khmer Rouge was paranoid about Vietnamese aggression, and decided to attack Vietnamese provinces with Khmer populations. He also slaughtered Vietnamese in Cambodia.
During the late Cold War, the Communist side was split into two rival teams, Soviet and China. Cambodia was on team China, Vietnam was on team Soviet.
Second. The U.S., who had just lost South Vietnam, did not want the now-unified Vietnam to spread their Marxism to South East Asia. During the 80's, the U.S. was also on friendly terms with China (probably because they hated Team Soviet more), and since China was on Khmer Rouge's side, the U.S. begrudgingly supported Khmer Rouge.
After the Vietnamese-Cambodia conflict, the Vietnamese appointed Hun Sen as head of a puppet government. Hun Sen remained Prime Minister to this day even after Cambodia found their king and restored him to the throne.