Despite a consensus at the highest levels of the US and British governments that it would be necessary " to liquidate Sukarno " , as related in a CIA memorandum from 1962 , and the existence of extensive contacts between anti-communist army officers and the US military establishment – training of over 1,200 officers , " including senior military figures " , and providing weapons and economic assistance – the CIA denied active involvement in the killings . Declassified US documents in 2017 revealed that the US government had detailed knowledge of the mass killings from the beginning , and was supportive of the actions of the Indonesian Army . US complicity in the killings , which included providing extensive lists of communist party officials to Indonesian death squads , has previously been established by historians and journalists . A top-secret CIA report from 1968 stated that the massacres " rank 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 early 1950s . " Support for Sukarno 's presidency under his " Guided Democracy " depended on his forced and unstable " Nasakom " coalition between the military , religious groups , and communists . The rise in influence and increasing militancy of the Communist Party of Indonesia ( PKI ) , and Sukarno 's support for it was a grave concern for Muslims and the military , and tension grew steadily in the early and mid-1960s . The third-largest communist party in the world , the PKI had approximately 300,000 cadres and full membership of around two million . The party 's assertive efforts to speed up land reform frightened those who controlled the land and threatened the social position of Muslim clerics . Sukarno required government employees to study his Nasakom principles as well as Marxist theory . He had met with Zhou Enlai , Premier of the People 's Republic of China , and after this meeting had decided to create a militia , called a Fifth Force , which he intended to control personally . Sukarno ordered weapons from China to equip this Fifth Force . He declared in a speech that he favoured revolutionary groups whether they were nationalist , religious or communist , stating " I am a friend of the Communists because the Communists are revolutionary people . " He said at a Non-Aligned Movement summit meeting in Cairo in October 1964 that his current purpose was to drive all of Indonesian politics to the left and thereby to neutralise the " reactionary " elements in the army that could be dangerous for the revolution . Sukarno 's international policies increasingly reflected his rhetoric
purges of the 1930s
Great Purge
Indonesian mass killings of 1965–66