Norodom Sihanouk in the context of "1970 Cambodian coup d'état"

Pol Pot (born Saloth Sâr; 25 May 1925 – 15 April 1998) was a Cambodian politician, revolutionary, and dictator who ruled the communist state of Democratic Kampuchea from 1975 until his overthrow in 1979. During his reign, his administration oversaw mass atrocities and he is widely believed to be one of the most brutal despots in modern world history. Ideologically a Maoist and Khmer ethnonationalist, Pot was a leader of Cambodia's Communist movement, known as the Khmer Rouge, from 1963 to 1997. He served as General Secretary of the Communist Party of Kampuchea from 1963 to 1981, during which Cambodia was converted into a one-party state. Between 1975 and 1979, the Khmer Rouge perpetrated the Cambodian genocide, in which an estimated 1.5–2 million people died—approximately one-quarter of the country's pre-genocide population. In December 1978, Vietnam invaded Cambodia to remove the Khmer Rouge from power. Within two weeks Vietnamese forces occupied most of the country, ending the genocide and establishing a new Cambodian government, with the Khmer Rouge restricted to the rural hinterlands in the western part of the country.

Born to a prosperous farmer in Prek Sbauv, French Cambodia, Pol Pot was educated at some of Cambodia's most elite schools. Arriving in Paris in October 1949 on an academic scholarship, he later joined the French Communist Party in 1951 while studying at École française de radioélectricité. Returning to Cambodia in 1953, he involved himself in the Khmer Viet Minh organisation and its guerrilla war against King Norodom Sihanouk's newly independent government. Following the Khmer Viet Minh's 1954 retreat into North Vietnam, Pol Pot returned to Phnom Penh, working as a teacher while remaining a central member of Cambodia's Marxist–Leninist movement. In 1959, he helped formalise the movement into the Kampuchean Labour Party, which was later renamed the Communist Party of Kampuchea (CPK). To avoid state repression, in 1962 he relocated to a jungle encampment and in 1963 he became the CPK's leader. In 1968, he relaunched the war against Sihanouk's government. After Lon Nol ousted Sihanouk in a 1970 coup, Pol Pot's forces sided with the deposed leader against the new government, which was bolstered by the United States military. Aided by the Viet Cong militia and North Vietnamese troops, Khmer Rouge forces advanced and controlled all of Cambodia by 1975.

Khmer Rouge is the name that was popularly given to members of the Communist Party of Kampuchea (CPK), and by extension to Democratic Kampuchea, which ruled Cambodia between 1975 and 1979. The name was coined in the 1960s by Norodom Sihanouk to describe his country's heterogeneous, communist-led dissidents, with whom he allied after the 1970 Cambodian coup d'état.

The Kampuchea Revolutionary Army was slowly built up in the forests of eastern Cambodia during the late 1960s, supported by the People's Army of Vietnam, the Viet Cong, the Pathet Lao, and the Chinese Communist Party (CCP). Although it originally fought against Sihanouk, the Khmer Rouge changed its position and supported Sihanouk following the CCP's advice after he was overthrown in a 1970 coup d'état by Lon Nol who established the pro-American Khmer Republic. Despite a massive American bombing campaign (Operation Freedom Deal) against them, the Khmer Rouge won the Cambodian Civil War when they captured the Cambodian capital and overthrew the Khmer Republic in 1975. Following their victory, the Khmer Rouge—who were led by Pol Pot, Nuon Chea, Ieng Sary, Son Sen, and Khieu Samphan—immediately set about forcibly evacuating the country's major cities. In 1976, they renamed the country Democratic Kampuchea.

The French protectorate of Cambodia (Khmer: ប្រទេសកម្ពុជាក្រោមអាណាព្យាបាលបារាំង; French: Protectorat français du Cambodge) refers to the Kingdom of Cambodia when it was a French protectorate within French Indochina, a collection of Southeast Asian protectorates within the French colonial empire. The protectorate was established in 1863 when the Cambodian King Norodom requested the establishment of a French protectorate over his country, meanwhile Siam (modern Thailand) renounced suzerainty over Cambodia and officially recognised the French protectorate on Cambodia.

Cambodia was integrated into the French Indochina union in 1887 along with the French colonies and protectorates in Laos and Vietnam (Cochinchina, Annam, and Tonkin). In 1947, Cambodia was granted self-rule within the French Union and had its protectorate status removed in 1949. Cambodia later gained independence. The day was celebrated as Independence Day on 9 November 1953 led by King Sihanouk and continued to rule as the leader of the nation until he was overthrown in 1970 by the US-led Khmer Republic of Lon Nol in a coup d'état before the rise of Angkar and the Khmer Rouge coming to power on 17 April 1975, following the Fall of Phnom Penh and the end of the Cambodian Civil War.

The Kingdom of Cambodia, also known as the First Kingdom of Cambodia, and commonly referred to as the Sangkum period, refers to Norodom Sihanouk's first administration of Cambodia, lasting from the country's independence from France in 1953 to a military coup d'état in 1970. Sihanouk continues to be one of the most controversial figures in Southeast Asia's turbulent and often tragic postwar history. From 1955 until 1970, Sihanouk's Sangkum was the sole legal party in Cambodia. After the 1970 coup, the semi-official name of Cambodia was State of Cambodia, it became a transitional government under a military dictatorship of Prime Minister Lon Nol against the Khmer Rouge and North Vietnamese.

Following the end of World War II, France restored its colonial control over Indochina but faced local resistance against their rule, particularly from Communist guerilla forces. On 9 November 1953, Cambodia achieved independence from France under Norodom Sihanouk but still faced resistance from Communist groups such as United Issarak Front. As the Vietnam War escalated, Cambodia sought to retain its neutrality but in 1965, North Vietnamese soldiers were allowed to set up bases and in 1969, the United States began a bombing campaign against North Vietnamese soldiers in Cambodia. The Cambodian monarchy was abolished in a coup on October 9, 1970 headed by Prime Minister Lon Nol, who established the Khmer Republic which lasted until the Fall of Phnom Penh to the Khmer Rouge led by Angkar ("Organization") when it came to power on 17 April 1975.

The Cambodian Civil War (Khmer: សង្គ្រាមស៊ីវិលកម្ពុជា, UNGEGN: Sângkréam Sivĭl Kâmpŭchéa) was a civil war in Cambodia fought between the Khmer Rouge, supported by North Vietnam and China, against the government of the Kingdom of Cambodia and, after October 1970, the Khmer Republic, which had succeeded the kingdom after a coup, both supported by the United States and South Vietnam. The conflict was part of the Vietnam War.

The conflict was linked to the Vietnam War. The North Vietnamese People's Army of Vietnam (PAVN) was involved to protect its bases in eastern Cambodia, which were crucial to its military effort in South Vietnam. This presence was initially tolerated by Prince Norodom Sihanouk, the Cambodian head of state, but domestic resistance combined with China and North Vietnam aiding the anti-government Khmer Rouge caused him to request help from the Soviet Union to stop this.

The Khmer Republic (Khmer: សាធារណរដ្ឋខ្មែរ, Sathearonaroat Khmae; French: République khmère) was a Cambodian state under the United States-backed military dictatorship of Marshal Lon Nol from 1970 to 1975. Its establishment was formally declared on 9 October 1970, following the 18 March 1970 coup d'état which saw the overthrow of Norodom Sihanouk's government and the abolition of the Cambodian monarchy.

The main cause of the coup was Norodom Sihanouk's tolerance of North Vietnamese military activity within Cambodia's borders; Vietnamese communist forces had gained de facto control over vast areas of eastern Cambodia as a result. Another important factor was the dire state of the Cambodian economy, an indirect result of Sihanouk's policies of pursuing neutrality.

The Khmer Rouge insurgency was an armed conflict in Cambodia and eastern border of Thailand that began in 1979 when the Khmer Rouge-ruled government of Democratic Kampuchea was deposed during the Cambodian–Vietnamese War. Between 1979 and the 1991 Paris Peace Agreements, the war was fought between the Vietnam-supported People's Republic of Kampuchea and an opposing coalition. After 1991, the unrecognized Khmer Rouge government and insurgent forces continued to fight against the new government of Cambodia from remote areas until their defeat in 1998. The remaining Khmer Rouge forces surrendered in 1999.

After the fall of the Khmer Rouge regime, Cambodia came under Vietnamese military occupation, and a pro-Hanoi, Soviet government known as the People's Republic of Kampuchea (PRK) was formed, led by the Kampuchean United Front for National Salvation. The conflict was fought during the 1980s between the People's Republic of Kampuchea and the Coalition Government of Democratic Kampuchea (CGDK). The latter was a government-in-exile formed in 1981 that was composed of three Cambodian political factions: the royalist FUNCINPEC party led by Prince Norodom Sihanouk, the Party of Democratic Kampuchea (often referred to as the Khmer Rouge), and the Khmer People's National Liberation Front (KPNLF). The Khmer Rouge representative at the UN, Thiounn Prasith, was maintained.

Lon Nol (Khmer: លន់ នល់, also លន់ ណុល; 13 November 1913 – 17 November 1985) was a Cambodian military officer and politician who served as Prime Minister of Cambodia twice (1966–1967; 1969–1971), as well as serving repeatedly as defence minister and provincial governor. As a right-wing nationalist, he led the military coup of 1970 against Prince Norodom Sihanouk, abolished the monarchy, and established the short-lived Khmer Republic. Constitutionally a semi-presidential republic, Cambodia was de facto governed under a military dictatorship. He was the commander-in-chief of the Khmer National Armed Forces during the Cambodian Civil War and became President of the Khmer Republic on 10 March 1972. On 1 April 1975, as the only president of the republic 16 days before Angkar and the Khmer Rouge captured Phnom Penh, Lon Nol fled to Indonesia and later the United States, first to Hawaii and then to California, where he remained until his death in 1985.