On this day in history

November 12, 1927

1927 - Joseph Stalin became the undisputed ruler of the Soviet Union. Leon Trotsky was expelled from the Communist Party leading to Stalin coming to power.

Stalin later entered into the Molotov–Ribbentrop Pact *, officially known as the Treaty of Non-Aggression between Germany and the Union of Soviet Socialist Republics

In addition to stipulations of non-aggression, the treaty included a secret protocol dividing Northern and Eastern Europe into German and Soviet spheres of influence, anticipating potential "territorial and political rearrangements" of these countries.

This mutual aid agreement was later to become one of history's more famous failed alliances.

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* The article also discusses Stalin's publication of the Falsifiers of History.