What sequence of events started World War 1?

World War I began with the assassination of Archduke Franz Ferdinand of Austria-Hungary on June 28, 1914, by a Serbian nationalist. This event triggered a series of diplomatic crises, leading Austria-Hungary to issue an ultimatum to Serbia. When Serbia's response failed to satisfy Austria-Hungary, it declared war on July 28, 1914. The conflict quickly escalated as alliances between major powers, including Germany, Russia, and France, drew multiple nations into a full-scale war.