At the start of World War I in 1914, the major alliances were divided into two sides: the Central Powers and the Allied Powers. Here’s a breakdown of the countries involved on each side, as well as some neutral nations:
Central Powers
- Germany
- Austria-Hungary
- Ottoman Empire (now Turkey)
- Bulgaria (joined in 1915)
Allied Powers
- France
- United Kingdom
- Russia (until 1917, when they withdrew due to the Bolshevik Revolution)
- Italy (joined in 1915, was initially part of the Triple Alliance with Germany and Austria-Hungary but switched sides)
- United States (joined in 1917)
- Japan
- Belgium
- Serbia
- Greece (joined in 1917)
- Portugal
- Romania (joined in 1916)
Neutral Countries
- Switzerland
- Spain
- Netherlands
- Norway
- Sweden
- Denmark
- Iceland
These lists are not exhaustive, as many other nations had varying degrees of involvement and allegiances. Neutral countries often remained outside the conflict for various political or geographic reasons.