Formerly classified 1978 US diplomatic cables released by Wikileaks show that the US government essentially supported the Khmer Rouge, in order to maintain “stability” in Cambodia and weaken the Vietnamese communists.

The US sent a cable to six US embassies in Asia on 11 October 1978 stating, “We believe a national Cambodia must exist even though we believe the Pol Pot regime is the world’s worst violator of human rights.”

The Phnom Penh Post continues:

Yet while the US government was aware of the horrific actions of the Pol Pot regime, with a July 21 cable from the US Embassy in Laos estimating 2 million people had died at its hands, it refused overtures from the country’s previous leadership to challenge the Pol Pot government’s right to represent Cambodia at the United Nations.

A 16 December US State Department cable to the UN insisted, “If the Pol Pot regime was toppled, this could result in indefinite guerrilla warfare in Cambodia.”

The US government insisted that, in spite of the roughly 1 to 2 million people killed by the Khmer Rouge, Pol Pot maintained “stability” in Cambodia, and that was most important.

Renowned muckraking journalist John Pilger, who witnessed firsthand the brutality of Pol Pot’s regime, has detailed how the US and UK helped give rise to the Khmer Rouge.

Pilger explained in detail in 2000:

Declassified United States government documents leave little doubt that the secret and illegal bombing of then neutral Cambodia by President Richard Nixon and Henry Kissinger between 1969 and 1973 caused such widespread death and devastation that it was critical in Pol Pot’s drive for power. “They are using damage caused by B52 strikes as the main theme of their propaganda,” the CIA director of operations reported on 2 May 1973. “This approach has resulted in the successful recruitment of young men. Residents say the propaganda campaign has been effective with refugees in areas that have been subject to B52 strikes.” In dropping the equivalent of five Hiroshimas on a peasant society, Nixon and Kissinger killed an estimated half a million people. Year Zero began, in effect, with them; the bombing was a catalyst for the rise of a small sectarian group, the Khmer Rouge, whose combination of Maoism and medievalism had no popular base.

After two and a half years in power, the Khmer Rouge was overthrown by the Vietnamese on Christmas Day, 1978. In the months and years that followed, the US and China and their allies, notably the Thatcher government, backed Pol Pot in exile in Thailand. He was the enemy of their enemy: Vietnam, whose liberation of Cambodia could never be recognised because it had come from the wrong side of the cold war. For the Americans, now backing Beijing against Moscow, there was also a score to be settled for their humiliation on the rooftops of Saigon.

To this end, the United Nations was abused by the powerful. Although the Khmer Rouge government (“Democratic Kampuchea”) had ceased to exist in January 1979, its representatives were allowed to continue occupying Cambodia’s seat at the UN; indeed, the US, China and Britain insisted on it. Meanwhile, a Security Council embargo on Cambodia compounded the suffering of a traumatised nation, while the Khmer Rouge in exile got almost everything it wanted. In 1981, President Jimmy Carter’s national security adviser, Zbigniew Brzezinski, said: “I encouraged the Chinese to support Pol Pot.” The US, he added, “winked publicly” as China sent arms to the Khmer Rouge.

In fact, the US had been secretly funding Pol Pot in exile since January 1980. The extent of this support – $85m from 1980 to 1986 – was revealed in correspondence to a member of the Senate Foreign Relations Committee. On the Thai border with Cambodia, the CIA and other intelligence agencies set up the Kampuchea Emergency Group, which ensured that humanitarian aid went to Khmer Rouge enclaves in the refugee camps and across the border. Two American aid workers, Linda Mason and Roger Brown, later wrote: “The US government insisted that the Khmer Rouge be fed . . . the US preferred that the Khmer Rouge operation benefit from the credibility of an internationally known relief operation.” Under American pressure, the World Food Programme handed over $12m in food to the Thai army to pass on to the Khmer Rouge; “20,000 to 40,000 Pol Pot guerillas benefited,” wrote Richard Holbrooke, the then US assistant secretary of state.

I witnessed this. Travelling with a UN convoy of 40 trucks, I drove to a Khmer Rouge operations base at Phnom Chat. The base commander was the infamous Nam Phann, known to relief workers as “The Butcher” and Pol Pot’s Himmler. After the supplies had been unloaded, literally at his feet, he said: “Thank you very much, and we wish for more.”

In November of that year, 1980, direct contact was made between the White House and the Khmer Rouge when Dr Ray Cline, a former deputy director of the CIA, made a secret visit to a Khmer Rouge operational headquarters. Cline was then a foreign policy adviser on President-elect Reagan’s transitional team. By 1981, a number of governments had become decidedly uneasy about the charade of the UN’s continuing recognition of the defunct Pol Pot regime. Something had to be done. The following year, the US and China invented the Coalition of the Democratic Government of Kampuchea, which was neither a coalition nor democratic, nor a government, nor in Kampuchea (Cambodia). It was what the CIA calls “a master illusion”. Prince Norodom Sihanouk was appointed its head; otherwise little changed. The two “non-communist” members, the Sihanoukists, led by the Prince’s son, Norodom Ranariddh, and the Khmer People’s National Liberation Front, were dominated, diplomatically and militarily, by the Khmer Rouge. One of Pol Pot’s closet cronies, Thaoun Prasith, ran the office at the UN in New York.

In Bangkok, the Americans provided the “coalition” with battle plans, uniforms, money and satellite intelligence; arms came direct from China and from the west, via Singapore. The non-communist fig leaf allowed Congress – spurred on by a cold-war zealot Stephen Solarz, a powerful committee chairman – to approve $24m in aid to the “resistance”.

Until 1989, the British role in Cambodia remained secret. The first reports appeared in the Sunday Telegraph, written by Simon O’Dwyer-Russell, a diplomatic and defence correspondent with close professional and family contacts with the SAS. He revealed that the SAS was training the Pol Pot-led force. Soon afterwards, Jane’s Defence Weekly reported that the British training for the “non-communist” members of the “coalition” had been going on “at secret bases in Thailand for more than four years”. The instructors were from the SAS, “all serving military personnel, all veterans of the Falklands conflict, led by a captain”.

The Cambodian training became an exclusively British operation after the “Irangate” arms-for-hostages scandal broke in Washington in 1986. “If Congress had found out that Americans were mixed up in clandestine training in Indo-China, let alone with Pol Pot,” a Ministry of Defence source told O’Dwyer-Russell, “the balloon would have gone right up. It was one of those classic Thatcher-Reagan arrangements.” Moreover, Margaret Thatcher had let slip, to the consternation of the Foreign Office, that “the more reasonable ones in the Khmer Rouge will have to play some part in a future government”. In 1991, I interviewed a member of “R” (reserve) Squadron of the SAS, who had served on the border. “We trained the KR in a lot of technical stuff – a lot about mines,” he said. “We used mines that came originally from Royal Ordnance in Britain, which we got by way of Egypt with marking changed . . . We even gave them psychological training. At first, they wanted to go into the villages and just chop people up. We told them how to go easy . . .”

The Foreign Office response was to lie. “Britain does not give military aid in any form to the Cambodian factions,” stated a parliamentary reply. The then prime minister, Thatcher, wrote to Neil Kinnock: “I confirm that there is no British government involvement of any kind in training, equipping or co-operating with Khmer Rouge forces or those allied to them.” On 25 June 1991, after two years of denials, the government finally admitted that the SAS had been secretly training the “resistance” since 1983. A report by Asia Watch filled in the detail: the SAS had taught “the use of improvised explosive devices, booby traps and the manufacture and use of time-delay devices”. The author of the report, Rae McGrath (who shared a joint Nobel Peace Prize for the international campaign on landmines), wrote in the Guardian that “the SAS training was a criminally irresponsible and cynical policy”.

When a UN “peacekeeping force” finally arrived in Cambodia in 1992, the Faustian pact was never clearer. Declared merely a “warring faction”, the Khmer Rouge was welcomed back to Phnom Penh by UN officials, if not the people. The western politician who claimed credit for the “peace process”, Gareth Evans (then Australia’s foreign minister), set the tone by calling for an “even-handed” approach to the Khmer Rouge and questioning whether calling it genocidal was “a specific stumbling block”.

Khieu Samphan, Pol Pot’s prime minister during the years of genocide, took the salute of UN troops with their commander, the Australian general John Sanderson, at his side. Eric Falt, the UN spokesman in Cambodia, told me: “The peace process was aimed at allowing [the Khmer Rouge] to gain respectability.”

The consequence of the UN’s involvement was the unofficial ceding of at least a quarter of Cambodia to the Khmer Rouge (according to UN military maps), the continuation of a low-level civil war and the election of a government impossibly divided between “two prime ministers”: Hun Sen and Norodom Ranariddh.

The Hun Sen government has since won a second election outright. Authoritarian and at times brutal, yet by Cambodian standards extraordinarily stable, the government led by a former Khmer Rouge dissident, Hun Sen, who fled to Vietnam in the 1970s, has since done deals with leading figures of the Pol Pot era, notably the breakaway faction of Ieng Sary, while denying others immunity from prosecution.

Once the Phnom Penh government and the UN can agree on its form, an international war crimes tribunal seems likely to go ahead. The Americans want the Cambodians to play virtually no part; their understandable concern is that not only the Khmer Rouge will be indicted.

The Cambodian lawyer defending Ta Mok, the Khmer Rouge military leader captured last year, has said: “All the foreigners involved have to be called to court, and there will be no exceptions . . . Madeleine Albright, Margaret Thatcher, Henry Kissinger, Jimmy Carter, Ronald Reagan and George Bush . . . we are going to invite them to tell the world why they supported the Khmer Rouge.”