World War I involved 32 nations from 1914 to 1919. It redrew the world map and reshaped many borders in Europe.
The collapse of the Russian Empire created Poland, the Baltics, and Finland. The Austro-Hungarian Empire dissolved into Austria, Hungary, Czechoslovakia, and Yugoslavia. When the Ottoman Empire collapsed, Turkey was established. The German Empire became Germany, and Germany lost substantial territory outside Europe.
For more information about the history of World War I, visit The National WWI Museum and Memorial.