There is a degree of irony in the fact that an International People’s Tribunal on the profoundly traumatic events that occurred 50 years ago in Indonesia will be convened next month in The Hague, the capital of the old colonial power.

It would have been far better for an inquiry of this sort, with its aim of digging out the truth rather than indicting the culprits, to take place in Jakarta. But more than 17 years after the Suharto dictatorship crumbled, the events that enabled the general to ensconce himself in power continue to occupy a deeply disputed terrain in the national memory.

Which is not entirely surprising, given that Suharto’s path to absolute did not merely entail wading through a few puddles of blood. Between the beginning of October 1965 and the end of January 1966, Indonesia witnessed what a classified CIA report a couple of years later described as “one of the worst mass murders of the 20th century, along with the Soviet purges of the 1930s, the Nazi mass murders during the second World War, and the Maoist bloodbath of the 1950s.”

In hindsight, one can, of course, add several place-names to that list: For instance, Bangladesh, Cambodia and Rwanda. What makes the CIA’s description particularly poignant is the fact that the agency — and the United States more broadly — was very much complicit in the massacres.

The precise death toll remains unclear, with estimates ranging from 500,000 to more than a million. The events were sparked on Sept. 29, 1965, by a relatively small-scale rebellion by junior army officers whose ostensible aim was to pre-empt a military coup against Sukarno, Indonesia’s leader since independence from the Dutch.

The supposedly left-leaning colonels and majors captured and killed half a dozen generals.One of their targets escaped, but Suharto was not on the hit list, which has prompted suspicions that, having foreknowledge of the plot, he had somehow indicated that he wasn’t opposed to it.

He was certainly well positioned to take advantage of it, though, and the official propaganda of the Suharto years decreed that he was instrumental in thwarting an attempted takeover by the Communist Party of Indonesia (PKI).With a membership of more than three million, the PKI was at the time the largest party of its kind outside the communist world, allied with Sukarno as well as with Beijing (in the context of the Sino-Soviet split), but hardly prone to Maoism of the militant variety on the domestic front.

It wasn’t Sukarno’s only ally; though the wily leader, who was popular in his country (and more broadly in the Third World) was hardly a dedicated democrat. But he relied on a coalition that encompassed communists, nationalists and Islamists. There were, inevitably, political tensions between these disparate forces, not least in the context of land reforms that the PKI forcefully backed and conservative elements resolutely opposed.

Whether or not any members of the PKI hierarchy were involved to any extent in the junior officers’ plot, the party was clearly unprepared for the descent into barbarism that followed. The victims of the genocide included not just PKI members but more or less anyone suspected of harbouring leftist sympathies.

The military was instrumental in the massacres, but it had plenty of eager allies, not least among Islamist organizations such as Nahdlatul Ulama, which yielded Indonesia’s first elected president after Suharto’s overthrow, Abdurrahman Wahid. Colonel Sarwo Edhie, who reputedly led special forces tasked with eliminating communists and their sympathisers, was the father-in-law of Susilo Bambang Yudhoyono, who served as president until last year.

The military, meanwhile, continues to wield overweening power in Indonesia, and some of the militias associated with its excesses over the past half century remain assured of their impunity. Small wonder, then, that death threats are still not uncommon if anyone begins to get too close to the truth, and that the current president, Joko Widodo, who had indicated he would at least be willing to apologise on behalf of the state for the mass murder of 1965, has lately resiled from that position. There is some evidence that the CIA was inclined to assassinate Sukarno as early as 1955, the year of the non-aligned Bandung conference.

By 1962, with his anti-imperialist stance even more firmly entrenched, the US and Britain were both keen to eliminate him. In 1965, the US Embassy in Jakarta provided the army with a list of at least 5,000 PKI targets.

The filmmaker Joshua Oppenheimer, whose pair of extraordinary documentaries have shed unprecedented light on the events of 1965, suggested in The New York Times last week that were the US to come clean about its role in the monumental atrocities, the Indonesian state might be encouraged to follow suit.

It would be unwise to hold one’s breath. But the Hague tribunal may help to highlight that the crimes against humanity committed in the name of anti-communism deserve a place of dishonor alongside the outrages associated with communism.