World War I began on June 28, 1914 when Archduke Franz Ferdinand of Austria was assassinated by a Serbian nationalist. The war lasted from 1914 to 1918 and involved many of the world's leading powers who were divided into two alliances: the Allies and the Central Powers. The Allies, led by Britain, France, and later the United States, defeated the Central Powers, led by Germany and Austria-Hungary. Over four empires collapsed as a result of the war and the map of Europe was radically changed.