[1] He was active writing by the Japanese occupation in the early 1940s, as evidenced by one of his short stories, "Tanda Bahagia" ("Sign of Happiness"), being published in Asia Raja on 1 September 1944.

While there, he took up a position as a high school teacher and, in 1952, joined the leftist oriented Institute of People's Culture (Lembaga Kebudajaan Rakjat, or Lekra).

[6] In 1953 he published a collection of short stories, entitled Jejak Langkah (Footsteps);[7] that same year, he became the head of the North Sumatran branch of Lekra.

[5] The following year he released the stageplay Saijah dan Adinda, based on a story in Dutch author Multatuli's novel Max Havelaar.

[7] While a high school teacher, Siregar used his position to spot upcoming actors and direct them to Lekra's stage production company Dinamo.

[8] After the failed coup d'état  – described by the government as having been led by the Indonesian Communist Party – on 30 September 1965, leftists were hunted by the military and the general public, while such institutions were closed.