Semaun joined SI in 1914 and also ISDV in 1915, leading him to hold dual party membership. Semaun militantly advocated the communist ideas and pushed for the leftist turn of SI, competing with the more moderate position taken by the central SI leaders such as Tjokroaminoto.
Semaun joined SI in 1914 and ISDV in 1915, leading to his dual party membership. Semaun vigorously promoted communist ideas and urged the leftist shift within SI, opposing the more moderate stance taken by central SI leaders like Tjokroaminoto.