The immediate cause for the outbreak of the first World War was the assassination of Archduke Francis Ferdinand. This event took place on June 28, 1914, in Sarajevo, Bosnia. Ferdinand, who was the heir to the Austro-Hungarian throne, was assassinated by a Serbian nationalist named Gavrilo Princip. This act of political violence set off a chain reaction of events that led to the start of World War I. Austria-Hungary saw the assassination as a threat to its sovereignty and issued an ultimatum to Serbia, which Serbia rejected. This triggered a series of alliances between different nations, resulting in a full-scale war that engulfed the world. While there were other underlying causes for the war, such as militarism and nationalism, the assassination of Archduke Francis Ferdinand was the immediate trigger.