The event commonly recognized as the start of World War I is the assassination of Archduke Franz Ferdinand of Austria-Hungary on June 28, 1914. This assassination, carried out by Serbian nationalist Gavrilo Princip, led Austria-Hungary to declare war on Serbia, setting off a chain reaction of alliances and conflicts. The complex web of alliances, militarism, imperialism, and nationalism contributed to an already volatile situation in Europe, escalating tensions into a full-blown global conflict. This assassination marked a pivotal point in 20th-century history, ultimately transforming international relations and leading to massive loss of life and widespread destruction.