The historical event most associated with the rise of totalitarian regimes in the 20th century is World War II. The aftermath of the war, along with economic instability and social unrest, created conditions conducive to the emergence of totalitarian regimes in various countries. Leaders like Hitler in Germany and Stalin in the Soviet Union exploited these conditions to consolidate power, suppress dissent, and enforce strict governmental control over many aspects of life. Their regimes exemplified the dangers of unchecked authority and ideological extremism.