Vladimir Lenin, Joseph Stalin, Adolf Hitler, Mao Zedong, Fidel Castro, and Pol Pot. Together, they were responsible for the bloodiest century in world history. PragerU co-founder Allen Estrin explains why we created this 6-part series: to ensure we never forget history, lest we be doomed to repeat it. Learn the truth about these notorious dictators and the consequences of their murderous regimes—5 minutes at a time.

Watch more from PragerU’s Hall of Evil series, presented by Paul Kengor.