On June 28, 1914 Archduke Franz Ferdinand, heir to the throne of the Austro-Hungarian Empire, is assassinated in Sarajevo by a Serbian nationalist. On July 28 Emperor Franz Joseph of Austria-Hungary declares war on Serbia. On July 31 Russia, an ally of Serbia, orders a full mobilization of its armed forces. On August 1, Germany, an ally of Austria-Hungary, mobilizes its forces and declares war on Russia. On August 3 Germany declares war on France, Russia’s ally. On August 4 Germany invades neutral Belgium in order to outflank the French army. When Germany refuses to acknowledge Belgian independence, Great Britain declares war on Germany. On August 6 Austria-Hungary declares war on Russia.