On June 28, 1914, Ferdinand, the heir to the throne of Austria-Hungary, and his wife Sophia, visited the Bosnian city of Sarajevo. A group of conspirators waited in the streets. The conspirators were members of the Black Hand, a terrorist organization that wanted Bosnia to be free and come part of the Serbian kingdom. This caused havoc and aggression in the Austria-Hungarian society. On July 28, Austria-Hungary declared war on Serbia. It also caused a heated rivalry between the alliances and made Austria-Hungary alliance with Germany and Italy.

Assassination of Archduke Francis Ferdinand