The major world event that involved the assassination of Archduke Franz Ferdinand was the outbreak of World War I. On June 28, 1914, Ferdinand, heir to the Austro-Hungarian throne, was assassinated in Sarajevo by Gavrilo Princip, a member of the nationalist group known as the Black Hand. This event triggered a series of alliances and escalating tensions among European powers, eventually leading to the full-scale war in 1914. The conflict reshaped borders, economies, and societies, resulting in a profound impact on the political landscape of the 20th century and laying the groundwork for future global conflicts.