The assassination of Archduke Franz Ferdinand of Austria on June 28, 1914, was pivotal in escalating tensions leading to World War I. His murder by Gavrilo Princip, a Bosnian Serb nationalist, triggered a chain reaction of alliances and diplomatic entanglements. Austria-Hungary's declaration of war on Serbia set off a series of mobilizations and declarations, involving major European powers due to their existing treaties. As nations sided with either the Central or Allied Powers, the tensions that had been building throughout Europe erupted into a full-scale conflict, culminating in a war that would reshape borders and societies for decades to come.