World War I started on July 28, 1914, and continued for a period of four years. It ended on November 11, 1918.
WWI, also known as the "Great War," began when Archduke Franz Ferdinand was murdered by gunshots while returning from an official visit to the former City Hall of Sarajevo in Bosnia. The Archduke was heir to the imperial throne of the Austro-Hungarian Empire.
The royal assassination was carried out by a 19-year-old Serbian named Gavrilo Princip, who believed that killing Archduke Ferdinand would usher in a period of freedom for his people. WWI led to the deaths of over 16 million people, both civilian and military.