After the fall of the Khmer Rouge and the conflict with Vietnam, Cambodia's economic situation was disastrous. During the first six months of 1979, approximately 80,000 people fled from Cambodia to reach Thailand. Many refugees died as a result of
anti-personnel mines while attempting to cross into Thailand, and many of those who did survive were turned away by Thai authorities. The refugees were forced into camps, especially in
Preah Vihear province, where living conditions were precarious. Cambodia's food situation worsened further, with Vietnamese troops attacking during the rice harvest, and food stocks being looted by the two belligerent parties. From August 1979 onward, the exile of the Cambodians became truly cataclysmic. Over one million people driven by hunger moved to the Thai border. The Khmer Rouge also sent its worst-off troops to the
refugee camps where humanitarian aid, which flowed to the camps through the
Royal Thai Armed Forces, contributed to helping the Khmer Rouge troops get back on their feet. After the first wave of refugees came to Thailand, between 100,000 and 300,000 civilians remained sheltered in camps on the Thai border, along a strip of around 30 kilometres. Anti-Vietnamese forces were supplied by China, primarily with small arms, through Thailand. At the international level, the entry of Vietnamese troops into Cambodia was condemned by most countries under pressure from China and the U.S., which wished to prevent Vietnam from establishing itself as a dominant power in
Southeast Asia. The UN did not recognise the People's Republic of Kampuchea, and following a vote in November 1979, the body considered Democratic Kampuchea to be Cambodia's sole legitimate government. Starting in 1983,
Margaret Thatcher's government sent elements of the British SAS, the
Special Air Service, to train the Khmer Rouge in landmine technologies. The U.S. and UK also imposed an embargo on Cambodia, resulting in serious consequences for the economy. Thailand, which had been accepting refugees, opened the
Khao I Dang camp in
Sa Kaeo province on 19 November 1979, about ten kilometres from Cambodia where 150,000 people would soon arrive. Thailand intended to recruit all Cambodian men of military age to form a force capable of repelling a possible Vietnamese attack. Around 250,000 other Cambodians preferred to stay in no-man's land between the two countries. Prince
Norodom Sihanouk, placed under house arrest by the Khmer Rouge in 1976, was taken from his palace during the Vietnamese offensive to be evacuated by plane to China. In the summer, an armed group favourable to the former monarch, the
Movement for the National Liberation of Kampuchea (MOULINAKA), was founded on the border with Thailand to fight against the Vietnamese. Former
corvette operations captain, Kong Siloah, led it until his death in August 1980. Different groups of the
Khmer Serei, or "Free Khmers", that carried out guerrilla operations against the Khmer Rouge between 1975 and 1979, also organized themselves to fight the Vietnamese.
Son Sann, former prime minister of Sihanouk, brought together several Khmer Serei and soldiers who took refuge in the West to found the
National Front for the Liberation of the Khmer People (KPNLF). In April 1979, it had around ten thousand refugees transported by the Thai army to the mountainous region of
Sok Sann, opposite the province of
Chanthaburi, which he declared a "liberated zone" and from where he launched appeals to his compatriots. Son Sann contacted Norodom Sihanouk in January 1979 so that he could take over the leadership of his troops, but the prince refused on several occasions. In early 1981, Sihanouk created, with the support of
ASEAN countries, an organization intended to lead anti-Vietnamese resistance, known as the
National United Front for an Independent, Neutral, Peaceful, and Cooperative Cambodia (FUNCINPEC). Organized in March 1981, a group of his followers transported MOULINAKA troops to Khmer territory on the Thai border near the province of Surin. Former troops of Kong Siloah joined the prince's ten thousand supporters, with whom they founded the National Sihanoukist Army, which constituted the armed wing of FUNCINPEC. During the summer of 1979, the Khmer Rouge took advantage of the monsoon that hampered the movement of Vietnamese troops to reorganize themselves to launch offensives, renaming their armed forces the National Army of Democratic Kampuchea. In July, Pol Pot installed his new headquarters, Bureau 131, under the flank of Mount Thom. The Khmer Rouge benefited from the assistance of Thai special forces, which ensured the training and recruitment of the Khmer armed forces. Three Cambodian resistance movements against the Vietnamese invasion coexisted from 1981 onward. This included the Khmer Rouge and its National Army of Democratic Kampuchea, led by Pol Pot and numbering 20 to 30,000 men, Son Sann's KPNLF with 10,000 men, Each of these three movements extended their power over some Cambodian refugee camps. The Sihanoukist guerrillas had no supply problems, but their poor performance in the field prevented them from extending their authority to a significant number of civilians. The Vietnamese occupation force numbered around 200,000 troops in 1981. The U.S. gave the People's Republic of China a
carte blanche on the Cambodian problem and continued to recognize Democratic Kampuchea as the government of Cambodia, mostly to mark its opposition to the
USSR-supported Vietnamese occupation. The UK and U.S., through Thailand, supported the Khmer Rouge as well as other guerrilla movements against the Vietnamese. Under American leadership, the
World Food Program provided approximately US$12 million in food to the Khmer Rouge through the Thai army. The USSR appeared to be quite overwhelmed by the situation in Cambodia. By supporting Vietnam, the Soviet military gained access to the ports on the Vietnamese coast. The Soviet government was not very active in Cambodia, since their attention was monopolized at the same time by the
Euromissile crisis and the
War in Afghanistan. Atrocities committed by the Khmer Rouge seriously damaged their international credibility. To make them more presentable in the eyes of the international community, China urged them to ally themselves again with Norodom Sihanouk, a more acceptable personality in the eyes of the West. On the other hand, China and the U.S. only agreed to subsidize the Sihanoukist resistance if the prince formed an anti-Vietnamese coalition with the Khmer Rouge, which could provide him with troops. Sihanouk initially refused any idea of a new coalition with Pol Pot's men, as several of his children and grandchildren had disappeared between 1975 and 1979. However, in 1981, noticing that the Khmer Rouge were successfully resisting Vietnamese offensives to dislodge them from their strongholds, he agreed to ally with them again to have a chance to return to power. On 4 September 1981, Sihanouk, Khieu Samphân, and Son Sann published a joint statement announcing the formation of a coalition government to liberate Cambodia from "Vietnamese aggressors". With the need for broader unity against Vietnam, a unity that an explicit communist line would hamper, in December 1981, the Khmer Rouge established the
Party of Democratic Kampuchea to replace the
Communist Party of Kampuchea and
de jure abandoned
Marxism-Leninism to choose
democratic socialism. Under the encouragement of China, which threatened to stop delivering weapons. The three factions formed the Coalition Government of Democratic Kampuchea (GCKD) on June 21, 1982, in Kuala Lumpur. The new faction would be chaired by Sihanouk and recognized by the UN. Son Sann would become the Prime Minister and Khieu Samphân the Deputy Prime Minister responsible for foreign affairs. This government would be recognized by the international community (except for the communist Eastern Bloc and
COMECON countries) and maintained ambassadors to the UN and France. The GCKD served, in practice, as a political front to hide the international aid being given to the Khmer Rouge, which remained the most powerful military partner of the anti-Vietnamese coalition. Guerrilla movements continued to carry out their actions along the border with Thailand. Khmer Rouge troops continued to invest in remote and mountainous areas and install anti-personnel mines, which caused many casualties among the civilian population. Son Sann and Sihanouk's goal was to exist militarily and then weigh in on any future negotiations. The ongoing conflict unfolded on a seasonal schedule. Each year, during the dry season, the Vietnamese People's Army attacked guerrilla camps, sometimes penetrating far into Thai territory. During the rainy season, the absence of paved roads immobilized Vietnamese mechanized units. This allowed the guerrillas to launch incursions into Cambodian territory. Starting in 1984, the Vietnamese mobilized the Cambodian population in a vast enterprise of passive defense. For three months, six months, or a year, civilians were forced to build roads to the west of the country, fortify villages, cut down forests, and dig protective dikes along the Thai border and part of the border with Laos. The army of the People's Republic of Kampuchea, poorly motivated and forced to operate under the leadership of the Vietnamese army, suffered many desertions. Defensive measures organized by the Vietnamese army, built with the assistance of locals, were effective at repelling GCKD forces. The Khmer Rouge, the KPNLF, and the ANS were unable to regain their position within the country, where the presence of many Vietnamese in the cities and some camps further complicated their task. Vietnamese soldiers were also unable to put an end to the activities of the rebel movements, especially because China provoked Vietnam with border incidents – around 3,750 between 1979 and 1982 – in the
Tonkin region. Vietnam was forced to further reinforce its military personnel, which resulted in dependence on Soviet supplies. Military spending represented 20% of Vietnam's GDP. Vietnam would end up taking around 17.5% of military aid and 20% of economic aid provided by the USSR to the
Third World. The U.S. financed Son Sann's KPNLF to increase Vietnam's stagnation in Cambodia. The Vietnamese threat also allowed the KPNLF to strengthen military cooperation with ASEAN countries. By the mid-1980s, the Cambodian conflict reached a military stalemate and increasingly weighed on Vietnamese and Soviet finances. In April 1983, the
Vietnamese People's Armed Forces launched an offensive on the Cambodian-Thai border, provoking a response from the
Royal Thai Army, which shelled Vietnamese positions. In late 1984, the Vietnamese army attacked resistance bases with heavy weapons that it had not used for five years. In January 1985, the Vietnamese captured the Ampil base held by the FLNKP and the Phnom Malai base held by the Khmer Rouge which were on the border with Thailand. The Thai army retaliated and saw one of its helicopters shot down by the Vietnamese. This fighting provoked an additional exodus of refugees into camps in Thailand. Around 200,000 civilians fled to Thailand in 1985. On September 2, 1985, Pol Pot, having reached the age of sixty, announced his retirement and left command of the Armed Forces to Son Sen. However, he assigned himself the role of presidency of a "Higher Institute of National Defense", a position with vague responsibilities but which seemed to indicate that the former general secretary of the Communist Party of Kampuchea maintained leadership of the Khmer Rouge troops. Around 10,000 men remained in practice under the command of Pol Pot, who operated from a camp located in Thailand.
Ta Mok also led 10,000 men in the
O Trao region. Khieu Samphan and
Ieng Sary, in turn, commanded troops in the
Battambang region and in Thai territory. China, willing to put the USSR in difficult situations in the region, continued to fuel the Khmer Rouge rebellion without openly approving Pol Pot's "excesses" as it once had. == Peace process ==