World War 1 began after the assassination of Archduke Ferdinand of Austria-Hungary by a Serbian nationalist. This caused alliances between European powers to take sides, with the Central Powers of Germany and Austria-Hungary fighting against the Allied Powers of Britain, France, Russia and later the United States. Over 15 million soldiers and civilians lost their lives during the war before an armistice was signed in 1918. The war was followed by a worldwide influenza pandemic that killed approximately 50 million people.