as the "block within" strategy. The most apparent effect was the infiltration committed on a nationalist-religious organization Sarekat Islam (Islamic Union) which advocated a pan-islam stance and freedom from colonial rule. Many members including Semaun and Darsono were succeessfully influenced by radical leftist ideas. As a result, communist thoughts and ISDV agents were successfully planted in the largest Islamic organization in Indonesia. After the involuntary departure of several Dutch cadres, combined with the infiltration operations, the membership shifted from majority-Dutch to majority-Indonesian. Establishment At its 23 May 1920 congress in Semarang, the ISDV changed its name into Perserikatan Komunis di Hindia (PKH; the Communist Union of the Indies). Semaun became party chairman, and Darsono the vice-chairman. Its highest committee members were predominantly Dutch. The PKH was the first Asian communist party to become part of the Communist International, and Sneevliet represented the party at the 2nd World Congress of the Comintern in 1921. During this time, communist sympathizers were still considered part of Sarekat Islam itself. This posed a troubling dilemma in which communist members were considered cadres in an Islamist organization, two very opposing ideas. More and more Sarekat Islam members were becoming aware of communist infiltration tactics. In the period leading up to the Sarekat Islam's sixth congress in 1921, members decided to stop the infiltrations once and for all. Agus Salim, the organization's secretary, introduced a motion banning Sarekat Islam members from dual membership in other parties. The motion passed despite opposition from Tan Malaka and Semaun, forcing the communists to change tactics. The Dutch colonial authorities introduced more restrictions on political activity and Sarekat Islam decided to focus on religious matters, leaving the communists as the only active extremist organization. In 1922, whilst Semaun was attending Far Eastern Labour Conference in Moscow, Tan Malaka tried to turn a strike by government pawnshop workers into a national strike by all Indonesian labor unions. The plot failed and Malaka was arrested, given a choice between internal or external exile; he chose the latter and left for the Soviet Union. In May, Semaun returned after seven months in the Soviet Union and began to organize the labor unions into a single organization. In September, the Union of Indonesian Labour Organizations (Persatuan Vakbonded Hindia) was formed. At the fifth Comintern congress in 1924, it was emphasized that "the top priority of communist parties is to gain control of trades unions";