1914 — Austrian Archduke Francis Ferdinand and his wife are assassinated at Sarajevo by a Serbian Nationalist. Austria-Hungary demands that Serbia suppress anti-Austrian agitation. Austria-Hungary rejects a British peace initiative and declares war on Serbia. Germany, alarmed at Russian mobilization, declares war on Russia. Great Britain declares war on Germany, which refused to guarantee the neutrality of Belgium.

• World War I breaks out between the Allies (Britain, France, Russia, Belgium and Serbia) and the Central Powers (Austria-Hungary and Germany).
• Japan and Montenegro join the Allies and Turkey joins the Central Powers. Italy, Portugal, Rumania and the United States later side with the Allies.