The major consequence of the assassination of Archduke Franz Ferdinand on June 28, 1914, was the immediate and direct trigger for World War I. The archduke's murder by a Bosnian Serb nationalist in Sarajevo set off a chain of events, leading Austria-Hungary to issue an ultimatum to Serbia. This provoked a web of alliances and escalatory responses among major European powers, culminating in the declaration of war. The conflict resulted in immense loss of life, significant geopolitical changes, and the eventual downfall of several empires, profoundly shaping the 20th century and altering the course of history.