The start of World War I in 1914 was triggered by the assassination of Archduke Franz Ferdinand of Austria on June 28, 1914. The heir to the Austro-Hungarian throne was killed in Sarajevo by Gavrilo Princip, a member of the nationalist group known as the Black Hand. This event set off a chain reaction of diplomatic crises and military mobilizations among European powers. Austria-Hungary, backed by Germany, issued an ultimatum to Serbia, leading to declarations of war. The intricate system of alliances and militarism among the Great Powers escalated the situation, resulting in a global conflict that lasted four years.