The Indies Social Democratic Association was founded in 1914 by Dutch socialist Henk Sneevliet and another Indies socialist. The 85-member ISDV was a merger of the two Dutch socialist parties (the SDAP and the Socialist Party of the Netherlands), which would become the Communist Party of the Netherlands with Dutch East Indies leadership.^[42] The Dutch members of the ISDV introduced communist ideas to educated Indonesians looking for ways to oppose colonial rule.

Later on, ISDV saw the events of the October Revolution in Russia as an inspiration for a similar uprising in Indonesia. The organization gained momentum among Dutch settlers in the archipelago. Red Guards were formed, numbering 3,000 within three months. In late 1917, soldiers and sailors at the Surabaya naval base revolted and established soviets. Colonial authorities suppressed the Surabaya soviets and the ISDV, whose Dutch leaders (including Sneevliet) were deported to the Netherlands.

Around the same time, ISDV and communist sympathizers began infiltrating other political groups in the East Indies in a tactic known 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.