Joshua Oppenheimer’s 2012 documentary The Act of Killing follows a cabal of ageing hoodlums around the city of Medan, in north-west Indonesia. Between 1965 and 66, they had enthusiastically joined militias across the country that garrotted, stabbed and mutilated to death at least half a million suspected leftists. Almost half a century later, they bragged openly about their exploits to Oppenheimer, for state propaganda since the late 60s has lionised the killers as heroes, and demonised the victims as godless communist traitors to the nation.

This polemically cinematic film – the first of two he made about the massacres – has transformed awareness of these events in the west and galvanised debate within Indonesia. It has shone a light on acts of exceptional cruelty, and on their intimate connection with the thuggish political culture of Indonesia today. Oppenheimer felt, as he amassed the film’s footage, as if he had “wandered into Germany 40 years after the Holocaust, only to find the Nazis still in power”.

As an activist, Oppenheimer has focused his talents on dramatising the horror and toxic contemporary afterlives of the Indonesian mass murders. His films have raised consciousness of the killings, but do not address their historical context. Only a few brief on-screen paragraphs at the start of The Act of Killing sketch some of the key events: the imposition of military dictatorship in late 1965, the crackdown on the Indonesian left, the murder of perhaps as many as a million “communists” by the army and civilian death squads, the killers’ enjoyment of impunity in Indonesia since. Two new books, one by Geoffrey Robinson and the other by Jess Melvin, now fill out this history. Between them, these authors tell us why one of the worst blood-lettings of the 20th century took place, who was responsible, and why, until recently, these events garnered such little international attention.

Facebook Twitter Pinterest President Suharto with his wife, Tien, the Queen and Duke of Edinburgh at Buckingham Palace in 1979. Photograph: PA

Before he became a history professor, Robinson was Amnesty International’s head of research for Indonesia, and his book skilfully combines a human rights advocate’s anger with academic rigour. His story begins in the twilight of Indonesia’s colonisation by the Dutch and the Japanese, and takes in the turbulent first two decades after its independence in the 1940s. He describes the military saturation of Indonesian society during the war with the Dutch, and explains the country’s instability on the eve of the 1965 massacres, as three political forces (the excitable nationalist first president, Sukarno; the US-trained army; a huge Communist party influenced by the radical, defiant stance of Mao’s China) faced off. Robinson also narrates, in heartbreaking detail, the grotesque, predominantly non-mechanised violence of the killings: death by decapitation, disembowelling, stabbing, genital mutilation, impaling, strangling.

Robinson is concerned with wider culpability and points the finger particularly at the US and British governments

He adjudicates carefully between divergent interpretations of one of the most confusing events of the cold war: the alleged coup of 1 October 1965, in which six Indonesian generals were kidnapped and killed under mysterious circumstances. General Suharto – the second president, architect of the military crackdown of 1965-66 and of the dictatorial New Order that ruled Indonesia between 1966 and 1998 – accused the Indonesian Communist party of orchestrating the attempted putsch and used this allegation to justify exterminating the Communists “down to the roots”. It now seems likely that the coup was planned by a small, secretive cell within the Communist party and the army, but there was no widespread planning for state capture among the party’s rank and file. Only one aspect of the coup is clear: it became a pretext for “the killing of half a million people, mass incarceration of more than a million others, and the complete annihilation of the left”.

Though the scope of her book – which is focused on the evolution of the massacres in Aceh, a province in north Sumatra – is narrower than Robinson’s, Melvin makes an essential point about the violence. For decades, Suharto’s New Order government taught Indonesians that the killings were a “spontaneous” uprising “by the people”, fuelled by righteous anger at “Communist” treachery. Through hard work, determination and a stroke of archival luck (a boxful of documents that the Indonesian intelligence agency carelessly gave her), Melvin shatters Suharto’s 50-year-old propaganda story. The “Indonesian genocide files”, as she calls the intelligence archive, confirm a narrative of army culpability: the mass murders of 1965-66 could not have taken place without the army’s centralised operation to “carry out non-conventional warfare … [to] succeed in annihilating … together with the people” communists and their supporters.

Joshua Oppenheimer: 'You celebrate mass killing so you don't have to look yourself in the mirror' Read more

Robinson agrees that “without the army’s logistical and organisational leadership … the mass killings could not have happened”. But he is also concerned with wider culpability for the violence, and points the finger particularly at the US and British governments who – for reasons of cold war realpolitik – facilitated the army’s crackdown. They waged a devious campaign of psychological warfare before, during and after the massacres, in the hope of giving the army a pretext to act against the communists, and to suppress accurate reports of the murders. US diplomats and the CIA’s Indonesia station left little to chance: they gave the army money, mobile radio equipment and lists of Indonesian communists.

Robinson and Melvin demolish Indonesian state orthodoxy on the country’s modern history, undermining with cool historical detail the legitimacy of political authoritarianism after 1965. But these two books have an importance far beyond Indonesian studies. They revise our definition of genocide, draw conclusions about the close links between militarism and mass violence, and remind us forcefully of the nefarious interventions of western powers at cold war turning points.

• Julia Lovell’s latest book is Splendidly Fantastic: Architecture and Power Games in China (Strelka).



• The Killing Season: A History of the Indonesian Massacres by Geoffrey Robinson is published by Princeton. To order a copy for £23.76 (RRP £27.95) go to bookshop.theguardian.com or call 0330 333 6846. Free UK p&p over £10, online orders only. Phone orders min p&p of £1.99.

• The Army and the Indonesian Genocide: Mechanics of Mass Murder by Jess Melvin is published by Routledge. To order a copy for £115, go to guardianbookshop.com