The war to end all wars...
On June 28, 1914, Archduke Franz Ferdinand of Austria-Hungary and his wife, Sophie, Duchess of Hohenberg, visited the city of Sarajevo and were assassinated by Gavrilo Princip, a 20-year-old Yugoslav nationalist. The assassinations triggered World War 1, which broke out a month later when Austria-Hungary declared war on Serbia. A series of alliances resulted in a rapid expansion of hostilities as Russia honored its treaty obligation with Serbia and declared war. Germany entered the war on the side of Austria-Hungary, and France and Great Britain soon joined the conflict as allies of Russia and Serbia.
The Triple Entente vs. the Central Powers