On June 28, 1914, Archduke Franz Ferdinand of Austria-Hungary and his wife Sophie visited Sarajevo. Bosnia had been annexed by Austria-Hungary in 1908, but many of its people were ethnic Serbs who wanted to join the neighboring Kingdom of Serbia instead.

That morning, a group of young Bosnian Serbs financed by the nationalist movement Black Hand tried to assassinate the Archduke. Some froze when the motorcade passed. Others hesitated, thinking the crowd was too thick. 

One attacker threw a bomb at the Archduke's car, but it bounced off and exploded under the next vehicle, injuring several people but leaving the Archduke unharmed. Afterward, one of the conspirators, Gavrilo Princip, left the route discouraged. He stopped outside a café, believing the assassination attempt had failed.

Later that day, the Archduke insisted on visiting the wounded. His driver took a wrong turn onto a street where Princip, happened to be standing outside the cafe. The Archduke’s car stalled as it tried to reverse, giving Princip the perfect chance. He fired two shots, killing both the Archduke and his wife.

That single wrong turn set off a chain reaction that led to World War I.

The assassination lit the fuse, but the powder keg had been ready for years. Europe was bound by a tangled web of alliances, locked in military buildups, competing for empires, and inflamed by nationalism. Austria-Hungary wanted to crush Serbia, Russia moved to protect it, Germany supported Austria-Hungary, and France and Britain were drawn in.