1950s
Before the election of 1955, PKI favoured Sukarno's plans for 'guided democracy' and was an active supporter of Sukarno. In the 1955 elections PKI came fourth with 16% of the votes. It won 39 seats (out of 257) and 80 out of 514 in the Constituent Assembly.
Opposition to the continued Dutch control over Irian Jaya was an issue often raised by PKI during the 1950s.
In July 1957 there was a grenade attack on the PKI office in Jakarta. In the same month PKI made advances in municipal elections. In September the same year the Islamist Masyumi publicly demanded that PKI should be banned.
On 3 December trade unions, largely under control of PKI, started seizing control of Dutch-owned companies. These seizures paved the way for the nationalization of foreign-owned enterprises. The struggles against foreign capitalists gave the PKI the opportunity to profile itself as a national party.
In February 1958 a coup attempt was made by pro-U.S. forces amongst the military and the political right-wing. The rebels, based in Sumatra and Sulawesi, proclaimed a Revolutionary Government of the Republic of Indonesia (Pemerintah Revolusioner Republik Indonesia) on 15 February. This so-called Revolutionary Government immediately began arresting thousands of PKI members in the areas under their control. PKI supported the efforts by Sukarno to quell the rebellion, including introduction of martial law. The rebellion was eventually defeated.
In August 1959 there was an attempt on behalf of the military to prevent the holding of the PKI congress. However the congress was held as scheduled, and was addressed by Sukarno himself. In 1960 Sukarno launched the slogan Nasakom, an abbreviation of Nasionalisme (Nationalism), Agama (Religion), Komunisme (Communism). Thus the role of PKI as a junior partner in the Sukarno polity was institutionalized. The PKI welcomed the launching of the Nasakom concept, seeing it in terms of a multiclass united front.
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