Not long after its founding in November 1918, Mratchny joined the Nabat Confederation of Anarchist Organizations and helped it to establish an illegal printing press in Siberia.
"[3] As a member of the Nabat, he became an employee of the Cultural-Educational Department of the Revolutionary Insurgent Army of Ukraine (RIAU) and a distributor of the Makhnovist newspapers "Free Rebel" and "Path to Freedom".
[5] When the first congress of the Profintern was held in July 1921, the imprisoned Nabat members staged a hunger strike in order to attract the attention of visiting syndicalist delegates, who protested their treatment to Felix Dzerzhinsky and Vladimir Lenin.
[10] He further accused the Makhnovshchina of militarism and anti-intellectualism, denounced Makhno and other insurgent commanders for displaying dictatorial tendencies, and criticised the unilateral executions by the kontrrazvedka.
In 1934, Mratchny was appointed as editor of the Yiddish newspaper Fraye Arbeter Shtime, but he resigned soon after the defeat of the Republicans in the Spanish Civil War and largely withdrew from the anarchist movement, declaring that he "felt like a rabbi in an empty synagogue.