On June 28, 1914, a young man named Gavril Princip darted out of a crowd in a Bosnian city and fired two bullets into a car, killing two passengers. Who were they?

The two people killed in Sarajevo on that fateful day were Archduke Franz Ferdinand (Review), heir to the throne of the sprawling Austro-Hungarian Empire, and his wife, Sophie, the Duchess of Hohenburg. The couple was on an official state visit to Bosnia, a region annexed by the empire, which had inflamed tensions with neighboring Serbia. The assassin, 19-year-old Gavril Princip, was a member of a Serbian nationalist secret society known as the Black Hand, which sought to liberate Bosnia from Austro-Hungarian rule.

The assassination itself was a bizarre mix of luck and incompetence. An earlier attempt to kill the Archduke with a bomb had failed, injuring several bystanders but leaving the royal couple unharmed. Later that day, after visiting the wounded in the hospital, the Archduke's driver took a wrong turn, coincidentally stopping the car just a few feet from where Princip was standing. Seizing this second, improbable chance, Princip fired his pistol, fatally wounding both Franz Ferdinand and Sophie.

This single act of political violence is widely cited as the immediate catalyst for World War I. In response to the assassination, Austria-Hungary issued a severe ultimatum to Serbia. When Serbia refused to comply with all of the demands, Austria-Hungary declared war. A complex web of military alliances was triggered, and within weeks, the major powers of Europe were drawn into a devastating conflict that would reshape the map of the world and define the 20th century.