On this date in 1914

The one small act that was responsible for the 20th century -- all of it. This assassination leads to WWI. Which leads to the collapse of the old continental empires in the heart of Europe, and the emergence of Bolshevism in Russia. From the ruins of WWI emerged a young demagogue named Adolph Hitler, and from his "war of revenge" (revenge for Germany's humiliating loss in WWI) begun in 1939, come all of the power structures, collapse of remaining empires, and postcolonial wars and horror in much of the third world. So it's all there -- all of it -- unleashed by Princip's bullets.

From the Writer's Almanac:

It was on this day in 1914 that the Austrian Archduke Franz Ferdinand and his wife were shot and killed by a Bosnian revolutionary, an event that led to the start of World War I.

Ferdinand was the heir to the throne of the Hapsburg Empire, and Bosnia was one of the empire's most rebellious provinces. Many ethnic Serbians wanted to free Bosnia from Hapsburg rule and unite their country with neighboring Serbia.

Early in the morning, on this day in 1914, Ferdinand and his wife, Sophie, boarded a touring car that would carry them to Sarajevo's city hall. What they didn't know was that six Bosnian Serbs, members of an organization called the Black Hand, were planning an assassination attempt.

Ferdinand's car wasn't even half way to city hall when one of the assassins threw a grenade. The chauffeur sped up, and the bomb bounced off the side of the car, wounding 20 people in the cars behind. Ferdinand made it to City Hall unscathed, and he was greeted there as though nothing out of the ordinary had happened. The mayor began making a welcome speech, and Ferdinand interrupted him, pointing out that he'd just nearly been killed.

Instead of offering to protect the archduke with an army escort, the general in charge of security suggested they return to the train station along the straightest, widest road in the city, so that they could travel rapidly. Unfortunately, no one told the chauffeur about the change in plans. So Ferdinand and his wife got back into the car, and the chauffeur proceeded down the route that had been published in the paper that morning. Once he realized his mistake, the chauffer stopped and tried to back out of a narrow street.

The chauffeur just happened to have stopped the car a few feet away from one of the assassins, a 19-year-old named Gavrilo Princip, with a .38 Browning pistol in his pocket. Standing just a few feet away from the royal car, he fired only two shots, but that was enough to kill both the Austrian archduke and his wife.

One month after the assassination, Austria used the event as an excuse to declare war on Serbia, even though the nation of Serbia had nothing to do with the Bosnian Serbs who had carried out the assassination. Germany chose to back Austria in its attack. Russia declared that it would defend Serbia from the assault. By August, France had entered the war against Germany. And when Germany invaded Belgium, Great Britain got involved as well, having pledged to defend Belgium from any invaders.

That series of alliances led to the largest war ever conducted in history at that point — all set in motion by a single assassin.

Coincidentally, it was also on this day in 1919 that the Treaty of Versailles was signed, officially ending World War I.