The event that marked the start of World War I in 1914 was the assassination of Archduke Franz Ferdinand of Austria. On June 28, 1914, Ferdinand and his wife, Sophie, were shot dead in Sarajevo by Gavrilo Princip, a member of the nationalist group known as the Black Hand. This assassination triggered a series of diplomatic crises and alliances among European powers, leading to the declaration of war. Austria-Hungary's ultimatum to Serbia escalated tensions, and, by late July 1914, a complex web of alliances activated, resulting in a full-scale war involving many nations across the globe.