The US National Security Archive has published declassified materials regarding the events, which were published on Oct. 17 by the George Washington University. The documents were sourced from 30,000 pages on the subject from the US Embassy in Jakarta during 1964-1968, with more slated to be released in 2018.

Foreign Ministry spokesperson Arrmanatha Nasir told the press that the documents needed fact-checking. Meanwhile, Indonesian Institute of Sciences (LIPI) historian Asvi Warman Adam said the declassification of the US files could push the Indonesian government to pay more attention to the 1965 massacre, which remains a sensitive topic.

The documents reveal, among other things, that the US was aware of the killings, which began in October 1965 and resulted in 100,000 deaths of suspected PKI members and supporters by mid-December of that year. The intelligence included information on the key role of the Army and religious parties and organizations in the purge, as well as tidbits on who was actually behind the Sept. 30 movement, shedding some light on the rumored Chinese involvement.

What happened on Sept. 30, 1965?

The generally accepted version was that on Sept. 30, 1965, six Army generals were kidnapped, murdered and buried in Lubang Buaya, Jakarta. The PKI was blamed for the failed coup attempt, thus the G30S/PKI term. An Army special operations battalion quickly took control and captured PKI leaders. What followed was the systematic killing of PKI members and sympathizers from across the country from late 1965 until 1966.

The PKI was disbanded and communism and Marxist/Leninism as an ideology were banned.

Before 1965, relations between the Indonesian Armed Forces, particularly its Army, with the PKI was tense. Three years after Indonesian independence, a revolt was staged by the PKI under the People's Democratic Front (FDR) in Madiun, Central Java, which was ended by the Army. As the PKI later focused on its electoral struggle, it became the Army’s rival as a mass-based institution and winning at that with better political machinery, at least at the grassroots level, according to scholar Adam Schwarz. Just before Sept. 30, 1965, there was attempt by the PKI to arm civilians as the Fifth Force (Angkatan Kelima), practically threatening the military’s monopoly on such matters.

Why was the US interested in the communism movement in Indonesia?

The US was at that time involved in the Cold War, a high-strung ideological war with rival communist power USSR. Both were nuclear powers, which raised the threat of devastating nuclear war should a conflict break out.

The Cold War significantly influenced US foreign policy to maintain its sphere of interest free from communism. One prominent doctrine was the Truman doctrine, with its domino theory and containment policy. The domino theory meant that should one state fall to communism, other states in the area would follow. Therefore, a left-leaning state had to be secured so that the danger was contained, thus the containment policy.

In 1965, the US and the Soviet Union were also fighting a proxy-war in Vietnam, which was met with strong opposition from academics and the younger generation. A declassified letter dated Aug. 5 from former finance minister Sjafruddin Prawiranegara to former USAID administrator Edwin Fox revealed the former’s belief that the US was winning and “is following the only right path which leads … to a necessary containment of aggressive communism.” Sjafruddin justified the war by arguing that it was a necessary self-defense move against aggressive, atheism-like communism.

Indonesia was particularly significant as the PKI was the third-largest communist party in the world after those in the Soviet Union and China, risking the entire Southeast Asia descending further into communism. President Sukarno at that time was waging war against Western-imperialism, which he called Nekolim, resulting in a rather hostile sentiment against the US. An airgram dated December 21, 1965, from the US Embassy in Jakarta notes a “change of atmosphere”, “increasingly warm cordiality”, and “a fantastic switch” after the Sept. 30 movement. Commenting on the Army’s takeover of state news agency Antara, which the embassy called “long one of our most articulate and harmful enemies,” the report says that, “On the whole, a fresh breeze is blowing.”

Was the PKI actually behind the Sept. 30 movement?

Telegram 1516 from the US Embassy in Jakarta to the secretary of state on Nov. 20, 1965 revealed that US officials knew that PKI supporters and members killed in the large-scale Army-led purge had no role in the Sept. 30 movement.

The telegram reported of an Australian journalist who had talked to a high-ranking PKI member from Yogyakarta, as well as other members in Tegal and Purwokerto, Central Java, all of whom claimed to not know about the alleged coup. This despite the Yogyakarta PKI source being among the top 50 cadres in the city and supposedly knowledgeable about PKI matters.

Previously, Telegram 779A dated Oct. 18, 1965 contained the comment “most encouraging of all, there are more signs people actually … putting blame where it belongs,” insinuating the US Embassy’s belief that the PKI was to blame for the Sept. 30 movement. An earlier Telegram 971 dated Oct. 12, 1965 reported that the Indonesian Army had gathered papers that elaborated the PKI’s role in the Sept. 30 killings, which Sukarno refused to read.  Note that this was before news emerged from the Australian journalist.

However, according to Polish first secretary Andrzej Gradziuk, who talked to a PKI Central Committee member, only several key PKI members knew about the coup. The plan came from an outsider and there was no intention to kill the six Army generals. Sukarno was also supposed to back the PKI on Oct. 1 in suppressing a Generals’ Council plot, a scenario in which it was the Army generals who were plotting against Sukarno and that the PKI was the hero. Telegram 971 dated Oct. 12, 1965 confirmed that the Army had indeed planned to depose Sukarno, but it was unclear whether the plan was formulated prior to Sept. 30 1965 or after.

In short, it was not clear whether the Sept. 30 coup attempt was really carried out by the PKI. The Army and the source from the Polish Embassy believed the PKI was involved. Based on our readings, many, if not most, PKI members did not know about the coup.

Was China behind the Sept. 30 movement according to the US documents?

No. The documents reveal that efforts to blame China for the Sept. 30 events were made by the Army.

Telegram 222 from the US consul general in Hong Kong to the US Embassy in Jakarta dated April 27, 1966 confirmed that Chinese involvement in the Sept. 30 movement was a hoax. The report referred to an article published in the Army’s newspaper, Angkatan Bersendjata, on April 25 linking Chinese leader Mao Zedong with the aborted coup, explaining that the article was a verbatim translation of a satire article originally published in a Hong Kong daily on Dec. 16, 1965. In the purely fictitious article, Mao encouraged PKI leader Aidit to remove the generals, saying that Mao himself had killed more than 20,000 cadre and soldiers. Aidit was also supposedly promised military aid. In the article, Beijing had insisted on staging the coup on Sept. 30. The full article can be found in another document.

Telegram A673 states that the anti-China propaganda was motivated to protect Sukarno and to pin the blame on Sukarno’s closest allies, the PKI and China. The report author notes that, “We do not think the Chinese were a primary factor in the September 30 Movement.”

The same conclusion was found in the examinations of Chinese diplomatic cables during 1961-1965 by Taomo Zhou in an article titled “China and G30S” in the book Sept. 30 Movement and Asia -- Under the Shadow of Cold War, edited by Kurasawa Aiko and Matsumura Toshio. Chinese documents confirmed that there were talks and negotiations led by Air Force chief Omar Dhani to request military assistance from China, but it was for the Fifth Force (Angkatan Kelima) and there was no proof that the militia involved in the Sept. 30 movement used Chinese weapons. A report of a conversation between Mao and Aidit dated Aug 5, 1965 reveals a discussion about a plan to seize power, but the news about the Sept. 30 movement came as a surprise to Beijing, showing a lack of knowledge of the details of the alleged PKI plan.

The US documents describe the backlash against the Chinese minority in Indonesia for the alleged Chinese involvement in the Sept. 30 killings. Some of the backlash was directly led by the Army. In the aforementioned Telegram 779A dated Oct 18, 1965, Sutarto revealed a planned action at the Chinese Embassy. Sutarto was special assistant to Ruslan Abdulgani -- two-time minister under Sukarno’s administration.

Telegram 1425 from the US Embassy in Jakarta to the secretary of state dated Nov. 12, 1965 revealed that the communist purge continued in the provinces and an anti-Chinese riot occurred in Makassar, in which 90 percent of shops owned by Chinese-Indonesians were ransacked according to a Sulawesi source.  A December report mentioned systematic economic repression of Chinese-Indonesians, who had their liquid assets seized and rice mills and textile enterprises taken over by regional military commanders. As a response, Communist China suspended trade relations with Indonesia.

In Bali, stores owned by Chinese-Indonesians were burned, although it seems that only those affiliated to mainland China were burned and not the “non-red” or nationalist Kuomintang Chinese. The situation led to Chinese in Bali requesting to be evacuated from the Chinese Embassy in Jakarta.

What does the US know about the 1965 mass killings?

In the briefing, it is stated that diplomats in the US Embassy in Jakarta kept a record of which PKI leaders were being executed, and that US officials actively supported Indonesian Army efforts to destroy the country’s left-leaning labor movement. From the documents, it was obvious that the Army was leading the anti-communist campaign. Airgram A-353 dated Nov. 30 1965 mentioned Gen. Soeharto’s support of the killings in Central Java.

The first known knowledge was revealed in Telegram 779A dated Oct. 18, 1965. The telegram reported a conversation between an embassy official with Surtarto, special assistant to Ruslan Abdulgani -- two-time minister under Sukarno’s administration. Surtarto mentioned an “anti-PKI action” that was “extended … to other areas in addition to [Jakarta]: Medan, South Sumatra, Makassar” and that “Central Java is in turmoil,” the latter claim viewed as an exaggeration by the US Embassy.

Telegram A298 dated Oct. 23, 1965 reported that Adnan Buyung Nasution, then an assistant to the attorney general, confirmed that the Army had executed many communists but tried to hush it up, fearing Sukarno would use foreign reports against those who were crushing the PKI, i.e., the Army.

Telegram 1290 dated Nov. 1, 1965 described the tense atmosphere in Palembang, South Sumatra, on Oct 28-29. The telegram stated “reportedly 600 communists already jailed and arrests continuing” and the Army was rounding up communist oil workers union PERBUM and SOBSI officials.

A more detailed description of the situation in East Java was found in Telegram 194 from the US consul in Surabaya to Jakarta dated Nov. 4 1965. The telegram mentioned continuing “clean-up raids” and that some Surabaya villages were strongly communist, as well as the concerning situation in Blitar and Banyuwangi. The report mentioned that Madiun, Pacitan and Ponorogo had been brought under control. East Java Military commander Basuki Rachmat was reportedly comparing the Sept. 30 movement to the 1948 PKI rebellion in Madiun, and propaganda pictures showing the bodies of the six mutilated generals were circulating in Surabaya.

If previously the telegrams only used the words “killed” and “arrested,” Action Telegram 183 from the US consul in Surabaya to Jakarta dated Nov. 26 1965 contained the word “slaughter,” implying that the killings were occurring on a larger scale. The telegram reported the slaughter of communists by Nahdlatul Ulama’s youth wing Ansor in many areas in East Java. A source said the largest instance happened in Tulungagung, with as many as 15,000 suspected communists killed, but it was doubted by the US consul.

Airgram A-398 revealed that some PKI leaders’ confessions may have been falsified, including that of Njono, a PKI Politburo member. A Dec. 21 1965 report by embassy first secretary Mary Louise Trent noted Sukarno’s disagreement to the aggression against the PKI, which at that time was estimated to have resulted in 100,000 PKI deaths and 10,000 deaths in Bali alone. By the end of December 1965, the PKI killings in East Java continued but “in more discreet manner” and in Madiun, the PKI prisoners were “being delivered to civilians for slaughter.”

The Army’s “ironclad control” over Central Java remained strong until October 1966, a year after the alleged coup attempt.

Who was working with the Army?

According to several documents, the nationalist and religious parties. Action Telegram 183 from the US consul in Surabaya to Jakarta dated Nov. 26 1965 reported that the widespread slaughter was likened to a holy war against infidels, since communists were considered atheists in Indonesia. Preachers in a Muhammadiah mosque in Medan were issuing “licenses to kill” the PKI.

Telegram 1485 from the US Embassy in Jakarta to the secretary of state dated Nov. 18, 1965 stated that the Army was working with religious parties, both Muslim and Christian, as well as the right-wing of the Indonesian Nationalist Party (PNI). Clashes between the PKI and religious and nationalist parties in East Java were reported, as well as the killing of 200 PKI prisoners by Muslims in Bone. In Pasuruan, it was reported that the “military ... turning its back and allowing Moslems [to] continue [to] slaughter,” and by December the military was “releasing nightly 10 to 15 prisoners to Moslems for execution.” In Kudus, the Army's Para Commando Regiment (RPKAD) gathered Catholics and Muslims to “root-out” the PKI.

Telegram A298 dated Oct. 23, 1965 included a memorandum of conversation with Adnan Buyung Nasution. Nasution argued that this was an opportunity for moderates “to redirect the course of the country’s fortunes,” implying that moderate groups were also working with the Army.

Was the US government helping the Indonesian Army in the mass communist killing?

A letter from political advisor to the commander-in-chief for the Pacific (CINCPAC) Norman Hannah to then US ambassador to Indonesia Marshall Green dated Oct. 13, 1965 discussed possible US aid to the Army. Hannah stated that there was “a reasonable possibility that the Indonesian Army might request our help against a PKI insurgency.” Mentioned in the briefing page, but not in the document, was Green’s request to the Lyndon B. Johnson administration to “explore [the] possibility of short-term one shot aid on covert, non-attributable basis” as a sign of US support. Green’s request was the first sign of the US’ possible contribution to the communist purge, but did not signify any concrete aid.

What else is in the documents?

• The documents also revealed the US’ knowledge of a brutal military crackdown in Papua. Telegram 542A dated Sept. 15, 1965 described Indonesian soldiers “[spraying] bullets at any Papuan in sight and many innocent travelers gunned down” following a flag-raising ceremony.
• While discussing Ruslan Abdulgani’s appointment as Indonesia’s permanent delegate to the United Nations, foreign minister Adam Malik argued that Soeharto made the decision upon listening to his dukun (soothsayer), who was paid off by Ruslan’s party, the PNI. Soeharto was rumored to be a superstitious man.
• An interesting conversation took place when the Army was rounding up suspected communists at a Shell oil refinery. Two domestic servants at a Dutch house were to be arrested. But the Dutchman said, “But not until lunch. I’ve got a big party planned.” The arrest waited until after lunch.
• A report made after Soeharto became president goes on in great length to describe Javanese culture and behavior, commenting that the great cultural differences presented basic problems in US conduct in Indonesia.