What are the causes of the Cambodian Civil War?

Answer 1

There are two different Cambodian Civil Wars. The more famous Cambodian Civil War was from 1968-1975. A second, less famous Cambodian Civil War of 1979-1999 followed. The intervening period of 1975-1979 was the period of Khmer Rouge rule of Cambodia during which Pol Pot's infamous genocide took place.

Cambodian Civil War of 1968-1975
The more famous Cambodian Civil War was from 1968-1975. During this period, the Kingdom of Cambodia was allied with the United States, Thailand, and South Vietnam in opposing the North Vietnamese in the Vietnam War. However, this conflicted with the needs and agenda of the North Vietnamese and the VietCong (South Vietnamese guerrillas who opposed the South Vietnamese government and sought unification with North Vietnam). Within Vietnam, the United States was relatively effective in preventing supply shipments from North Vietnam to the VietCong. As a result, the North Vietnamese and VietCong created supply trails that led through Laos and Cambodia. These were termed the "Ho Chi Minh Trails".

The Kingdom of Cambodia resisted this incursion of their territory by their enemies, which made the Ho Chi Minh trails perilous. In order to have protection from the Kingdom of Cambodia's forces, North Vietnam and the VietCong supported the weak Communist-aligned paramilitary called the Khmer Rouge by giving them an influx of money and funds. This resulted in the Khmer Rouge being able to become much more of a threat to the Kingdom and the Kingdom expanded its role to combat it.

Other international players exacerbated the fighting. The US participated in order to protect South Vietnam, prevent the rise of Communism in Cambodia, and to buy time for the withdrawal of US troops from Vietnam. Both North and South Vietnam also participated in the fighting. After five years of savage fighting, the Kingdom of Cambodia was overthrown on 17 April 1975 when the victorious Khmer Rouge proclaimed the establishment of Democratic Kampuchea. This would be the infamous regime headed by Pol Pot which was responsible for the genocide of between 1.5-2.2 million Cambodians.

Cambodian Civil War of 1979-1999
Pol Pot and the Khmer Rouge, in addition to the violence perpetrated against their own people, launched an offense into the now-unified Vietnam. For a few years, the Vietnamese (the former North Vietnamese government) tolerated it in recognition of their historic support for the Khmer Rouge in the previous Cambodian Civil War for nearly four years. However, in 1979, the Vietnamese government decided to retaliate by launching a full-scale invasion of Cambodia and overthrowing the Khmer Rouge. They replaced it with a Vietnamese puppet government called the People's Republic of Kampuchea. The Khmer Rouge joined two other paramilitaries, one of which was FUNCINPEC, made up of those loyal to the former Kingdom of Cambodia. These three paramilitaries (of which the Khmer Rouge was the strongest) became enemies of the regime and actively engaged in violence against the new PRK, forming the Coalition Government of Democratic Kampuchea. Even though the CGDK had assistance from the US, UK, and Thailand (all of which sought to limit Vietnamese influence in Southeast Asia), the PRK had control of most of the major population centers of Cambodia, penning the CGDK in the northwest area of the country, near Siem Reap and Battambang. Even though the war was, generally speaking, regionally contained, it continued for nearly 20 years before the UN-sponsored Paris Peace Agreement of 1991 ended the conflict and restored the Kingdom of Cambodia, while providing amnesty to most leaders from both the PRK and CGDK.

A serious and unfortunate consequence of this peace agreement is that most of the perpetrators of the Cambodian genocide later became part of the leadership of CGDK, making them immune to war crimes prosecution. To date, only one of the numerous aides and facilitators of the genocide has been subjected to an international tribunal.