The First World War re-shaped Europe, not least in Russia, where revolution had erupted in 1917. A far greater upheaval than most thought possible led to the collapse of autocratic Russia, the execution of the Tsar and his family, and the Bolshevik seizure of power.
The new Communist state which replaced Russia was named the Union of Soviet Socialist Republics. Led by Lenin, it changed the entire world. The Russian Revolution shaped the remainder of the 20th century, with a critical role in the Second World War and the Cold War.