The assassination of Archduke Franz Ferdinand occurred on June 28, 1914. This event was pivotal in igniting World War I, as it set off a chain reaction of alliances and militaristic responses across Europe. The murder, committed by a Bosnian Serb nationalist, led Austria-Hungary to issue an ultimatum to Serbia, which escalated tensions. Subsequently, the intricate system of alliances among European powers activated, causing a widespread conflict that resulted in millions of casualties and significant geopolitical changes. This assassination is often cited as the catalyst that plunged Europe into a devastating war.