The outbreak of World War I was triggered by the assassination of Archduke Franz Ferdinand of Austria-Hungary in Sarajevo, Bosnia, on June 28, 1914. The assassin, Gavrilo Princip, belonged to a Serbian nationalist group that sought independence from Austria-Hungary. In response to the assassination, Austria-Hungary declared war on Serbia on July 28, 1914. This act set off a series of interconnected alliances and subsequent declarations of war among European powers, escalating the conflict into a full-scale global war. The assassination and the ensuing chain reaction of events marked a pivotal moment in history, leading to one of the deadliest and most far-reaching conflicts the world had ever witnessed.