The major event that sparked the beginning of World War I was 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 assassination set off a chain reaction of alliances and treaties, leading Austria-Hungary to declare war on Serbia. The resulting entanglement of alliances among the major European powers escalated the conflict, eventually pulling in nations across the world and leading to the large-scale war known as World War I, which lasted until 1918.