In Winston Churchill's "Blood, Toil, Tears, and Sweat" speech, delivered on May 13, 1940, shortly after he became Prime Minister of the United Kingdom, the phrase "monstrous tyranny" refers to Nazi Germany and its oppressive regime under Adolf Hitler. At the time, Germany was engaged in aggressive military campaigns across Europe, committing atrocities and suppressing freedom in occupied countries.
When Churchill speaks of this tyranny as "never surpassed in the dark and lamentable catalogue of human crime," he is highlighting the severity and brutality of the actions taken by the Nazi regime. This phrase emphasizes that the crimes committed under Hitler's rule—including genocide, war crimes, and other forms of oppression—are among the worst in history. Churchill is invoking a sense of moral urgency and the need for resistance against such evil. He recognizes the historical weight of their actions and frames the struggle against Nazi Germany as a critical and noble cause for humanity.