The communist propaganda was extensively based on the Marxism-Leninism ideology to promote the Communist Party line. In societies with pervasive censorship, the propaganda was omnipresent and very efficient. It penetrated even social and natural sciences giving rise to various pseudo-scientific theories like Lysenkoism, whereas fields of real knowledge, as genetics, cybernetics, and comparative linguistics were condemned and forbidden as "bourgeois pseudoscience". With "truths repressed, falsehoods in every field were incessantly rubbed in in print, at endless meetings, in school, in mass demonstrations, on the radio".
Main Soviet censorship body, Glavlit employed seventy thousand full-time staff not only to eliminate any undesirable printed materials, but also "to ensure that the correct ideological spin was put on every published item". Telling anything against the "Party line" was punished by imprisonment. "Today a man only talks freely to his wife - at night, with the blankets pulled over his head", said writer Isaac Babel privately to a trusted friend.
According to Robert Conquest, "All in all, unprecedented terror must seem necessary to ideologically motivated attempts to transform society massively and speedily, against its natural possibilities. The accompanying falsifications took place, and on a barely credible scale, in every sphere. Real facts, real statistics, disappeared into the realm of fantasy. History, including the History of the Communist Party, or rather especially the history of the Communist Party, was rewritten. Unpersons disappeared from the official record. A new past, as well as new present, was imposed on the captive minds of the Soviet population, as was, of course, admitted when truth emerged in the late 1980s".