In the 20th century, European nations formed competing military alliances. War finally broke out in 1914 when a Serbian nationalist assassinated the heir to the throne of Austria. Austria went to war against Serbia, and many other countries joined in. On one side were the British, the French and Russian empires, Italy, and Japan (the Entente Powers). On the other side were the Germans, Austrians, Hungarians, Bulgarians, and Turks (the Central Powers).