- The Treaty of Versailles and other peace treaties that ended the war and redrew the map of Europe.
- The dissolution of the Ottoman and Austro-Hungarian empires, as well as the German Empire.
- The creation of new nation-states, including Poland, Czechoslovakia, and Yugoslavia.
- The Russian Revolution and the establishment of the Soviet Union.
- The rise of fascism and communism in Europe.
- The Great Depression, a global economic crisis that began in the United States in 1929.
- World War II, which began in 1939.