On June 28, 1914, Archduke Franz Ferdinand of Austria-Hungary and his wife Sophie are assassinated while visiting Sarajevo. Ferdinand was the heir presumptive of the throne of the Austro-Hungarian Empire, meaning he was at the time next in line to rule the country barring the birth of another heir with a better claim. The assassination was perpetrated by members of the Young Bosnia movement and the Black Hand society. The initial attempt saw the conspirators attempt to bomb Ferdinand's motorcade; however, the bomb bounced of Ferdinand's car and knocked-out one of the following vehicles. Not long afterward, Ferdinand cancelled his original plans to instead visit the wounded at the hospital. Along the way, his driver took a wrong turn and quickly stopped in order to turn around after learning of his mistake. Unfortunately, the car stopped in front of Gavrilo Princip, one of the assassins from the failed attempt earlier in the day. Princip proceeded to walk up to the car and open fire with an FN M1910 pistol, striking Franz Ferdinand and Sophie before being disarmed while attempting to take his own life. Within minutes, both were dead.

The assassination came at a time of high tensions and secret mutual defense agreements among the nations of Europe. Austria, fully supported by Germany, issued a list of demands (known as the July Ultimatum) that were to be accepted by the Serbians within 48 hours or Austria would take action. In turn, Russia assured Serbia of its support and France agreed. When Serbia refused to compromise on certain points, particularly a demand to allow Austrian police to operate in Serbia, all sides began to prepare their forces for war. On July 28, Austria declared war on Serbia. In the days that followed, Germany & Austria-Hungary would officially be at war with France, Russia, Britain, and Serbia. World War I had begun and over the course of the next four years an estimated 16 million military personnel and civilians would die.