19171920

19171920 refers to the historical span from the year 1917 through 1920. During these years the world experienced the dissolution of empires, dramatic political revolutions, and the early attempts to construct a new international order in the aftermath of World War I.

In 1917 the Russian Empire collapsed as the February and October revolutions brought the Bolsheviks to power. The same year marked the United States entering World War I, shifting the war's balance. In 1918 the Armistice ended fighting on the Western Front, and the Treaty of Brest-Litovsk with the Central Powers marked Russia's exit from the war. The period also saw a deadly influenza pandemic and ongoing domestic upheavals in many countries.

1919 yielded the Paris Peace Conference and the signing of the Treaty of Versailles and other treaties that redrew many borders and established the League of Nations. National self-determination movements advanced in Europe and beyond, and new states emerged. Cultural and political upheavals accompanied these changes, including the Irish War of Independence, the May Fourth Movement in China, and the beginnings of the German Weimar Republic. The year 1920 continued the process with further treaties, the formal founding of the League of Nations, and the reconfiguration of postwar Europe and its economies.