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 . Having helped establish an underground group in 1918 , Chernyi joined another group called the Underground Anarchists the following year . The organization , which had been founded by Kazimir Kovalevich and Piotr Sobalev , published two issues of an incendiary broadsheet denouncing the Communist dictatorship as the worst tyranny in human history .