Allied Powers:
- Belgium
- British Empire
- France
- Greece (from 1917)
- Italy (from 1915)
- Japan
- Montenegro (from 1914 to 1916)
- Portugal (from 1917)
- Romania (from 1916)
- Russia (until March 1918)
- Serbia
- United States (from 1917)
Central Powers:
- Austria-Hungary
- Bulgaria (from 1915)
- Germany
- Ottoman Empire