The commonly held notion that it was started out of outrage over the assassination of Archduke Franz Ferdinand of Austria and his wife Sophie at the hands of Serbian nationalist secret society known as the “Black Hand” isn’t entirely correct. In fact, the Emperor Franz Josef himself expressed relief over the assassination because it rid him of an heir whom he deeply disliked. The Emperor commented that “God will not be mocked. A higher power had put back the order I couldn’t maintain.”
Indeed, it wasn’t just the Emperor who was relieved; it was reported by an Austrian newspaper that the general consensus among the various political circles was that the assassination, though a tragedy, was for the best. As far as the Austrian people were concerned, it was noted “The event almost failed to make any impression whatever. On Sunday and Monday, the crowds in Vienna listened to music and drank wine as if nothing had happened.” Indeed, it took the government itself a full three weeks to react.
As you’ll see shortly, the “treaty alliance system” that was prevalent in Europe with numerous treaties interconnecting the various states was really at the heart of why what would have been a small conflict, not noteworthy in any way in history, escalated into one of the bloodiest wars in human history with over 15 million people dead. Somewhat ironically, the spark that set it all off was the assassination that nobody really cared about.
So why go to war over an assassination, if nobody cared? Because, while nobody seemed to much care about the assassination itself, Austria-Hungary had been looking for an excuse to wage a “preventative war” against Serbia as a state in order to weaken or destroy them so as to take back territory in the Balkans, which had been taken during the Balkan Wars. They had not taken it back up to this point because they lacked Germany’s support; without that support, they feared Russia too much, because of the treaty Russia