The so-called 'social revolutions' following the independence proclamation were challenges to the Dutch-established Indonesian social order, and to some extent a result of the resentment against Japanese-imposed policies. Across the country, people rose up against traditional aristocrats and village heads and attempted to exert popular ownership of land and other resources. The majority of the social revolutions ended quickly; in most cases the challenges to the social order were quashed, although in East Sumatra, the sultanates were overthrown and there were mass killings of members of the aristocratic families.
A culture of violence rooted in the deep conflicts that split the countryside during the revolution would repeatedly erupt throughout the whole second half of the 20th century. The term 'social revolution' has been applied to a range of mostly violent activities of the left that included both altruistic attempts to organise real revolution and simple expressions of revenge, resentment and assertions of power. Violence was one of the many lessons learned during the Japanese occupation, and figures identified as 'feudal', including kings, regents, or simply the wealthy, were often attacked and sometimes beheaded. Rape became a weapon against 'feudal' women. In the coastal sultanates of Sumatra and Kalimantan, for example, sultans and others whose authority had been shored-up by the Dutch, were attacked as soon as Japanese authority left. The secular local lords of Aceh, who had been the foundation of Dutch rule, were executed, although most of Indonesia's sultanates fell back into Dutch hands.
Most Indonesians lived in fear and uncertainty, particularly a significant proportion of the population who supported the Dutch or who remained under Dutch control. The popular revolutionary cry 'Freedom or Death' was often interpreted to justify killings under claimed Republican authority. Traders were often in particularly difficult positions. On the one hand, they were pressured by Republicans to boycott all sales to the Dutch; on the other hand, Dutch police could be merciless in their efforts to stamp out smugglers on which the Republican economy depended. In some areas, the term kedaulatan rakyat ('exercising the sovereignty of the people') – which is mentioned in the preamble of the Constitution and used by pemuda to demand pro-active policies from leaders – came to be used not only in the demanding of free goods, but also to justify extortion and robbery. Chinese merchants, in particular, were often forced to keep their goods at artificially low prices under threat of death.
On 18 September 1948 an 'Indonesian Soviet Republic' was declared in Madiun, east of Yogyakarta, by members of the PKI and the Indonesian Socialist Party (PSI). Judging the time right for a proletarian uprising, they intended it to be a rallying point for revolt against "Sukarno-Hatta, the slaves of the Japanese and America". Madiun however was won back by Republican forces within a few weeks and the insurgency leader, Musso, killed. RM
Suryo, the governor of East Java, as well as several police officers and religious leaders, were killed by the rebels. This ended a distraction for the revolution, and it turned vague American sympathies based on anti-colonial sentiments into diplomatic support. Internationally, the Republic was now seen as being staunchly anti-communist and a potential ally in the emerging global Cold War between the American-led 'free world' and the Soviet-led bloc.
Members of the Republican Army who had come from Indonesian Hizbullah felt betrayed by the Indonesian Government. In May 1948, they declared a break-away regime, the Negara Islam Indonesia (Indonesian Islamic State), better known as Darul Islam. Led by an Islamic mystic, Sekarmadji Maridjan Kartosuwirjo, Darul Islam sought to establish Indonesia as an Islamic theocracy. At the time, the Republican Government did not respond, as they were focused on the threat from the Dutch. Some leaders of Masjumi sympathised with the rebellion. After the Republic regained all territories in 1950, the government took the Darul Islam threat seriously, especially after some provinces declared that they had joined Darul Islam. The rebellion was put down in 1962.