the murder of a Dutch official in Tolitoli, Celebes which led to the arrest of an SI leader Abdul Muis. There was also a shooting incident in Garut, West Java in June 1919 which led to the arrest of SI leaders, including Sosrokardono and Tjokroaminoto who was prisoned in 1921 for 11 months. These events had led to the dramatic decrease in its membership, due to the fear of carrying a membership card leading to an arrest. Split The ideological rift between the Islamist wing led by Agus Salim and the communist wing led by Semaun intensified, at the expense of Tjokroaminoto's support level. Semaun was now effectively a leader of ISDV together with Darsono. ISDV metamorphosed into the Communist Association of the Indies (PKI) in 1920, as the direct predecessor of the Communist Party of Indonesia (PKI). During this time, labor and trade unions achieved considerable success in labor disputes and wage negotiations, leading to an attempt to establish the Labor Movement Association (PPKB) as a federation of PKI and SI unions in 1919 which comprised 22 unions and 72,000 members. Salim and Soerjopranoto, a labor activist belonged to the SI union and nicknamed as raja mogok (the strike king), competed with Semaun for the leadership of PPKB. Threatened by Semaun's influence, Salim denounced the dual party membership during the 1921 SI Congress. The conflict between Salim and Semaun's factions reached the highest point after Semaun's recruitment of several labor groups under the PPKB which were then absorbed into the PKI. Salim's motion to prohibit dual membership was officially adopted by the SI leaders including Salim and Muis in the subsequent SI Congress, leading to the effective expulsion of Semaun and his communist followers from the SI leadership. The decision led to the split of SI branches between the Islamist-supporting "White SI" and PKI-supporting "Red SI." The expelled left-wing faction of SI set up a group known as Sarekat Islam Merah (Red Islamic Association), which was later renamed to Sarekat Rakjat (People's Association) and served the mass organization of PKI. The split of communist members, in addition to the mounting pressure by the colonial government, had led to the severe decline of SI as an organization. Aftermath With the release of Tjokroaminoto from jail in May 1922, he decided to unify the ideological orientation and get rid of communist infiltration once and for all. In February 1923, SI reformed