The assassination of Archduke Franz Ferdinand on June 28, 1914, precipitated World War I, a major global conflict. The assassination set off a complex web of alliances and tensions among European powers. Austria-Hungary’s declaration of war against Serbia triggered Russia's mobilization in defense of Serbia, leading Germany to declare war on Russia. Ultimately, the intricate alliance system drew multiple nations into the conflict, with the Central Powers (Germany, Austria-Hungary, and later the Ottoman Empire) facing off against the Allies (France, Russia, Britain, and later the United States). This war reshaped global politics and borders.