In 1919 Chernyi joined a group called the Underground Anarchists, who published two numbers of a broadsheet which denounced the Communist dictatorship as the biggest tyranny in human history. On September 25, 1919, a little group of social revolutionaries and anarchists bombed the headquarters of the "Moscow Committee" of the Communist Party in protest at the growing repression. Twelve Communists were killed and forty-five others were mutilated. 