The Communist Party of Indonesia (PKI) was founded in 1920 and became one of the largest communist parties in the world outside the Soviet Union. It played a significant role in Indonesian politics, advocating for workers' rights and land reforms. The party gained substantial support in the 1950s and 1960s, particularly among the rural population. In 1965, a failed coup led to a violent anti-communist purge, resulting in the mass killing of PKI members and sympathizers. The party was subsequently banned, and its influence in Indonesian politics diminished significantly. The events surrounding the PKI remain a controversial topic in Indonesia's history.