There’s no telling what may be the catalyst that plunges the world into chaos. Saturday is the 100th anniversary of one of those pivotal moments.

On June 28, 1914, Archduke Franz Ferdinand and his wife, Sophie, fell victim to the assassin’s bullet. It was a fluke that the assassin, Gavrilo Princip, would encounter the motorcade that was carrying the royal party. After having survived an earlier assassination attempt, the archduke’s driver took a wrong turn and, while backing up, moved slowly past Princip, who killed the heir apparent to the Austro-Hungarian throne and his wife.

Those two deaths would be the first of more than 16 million lives claimed in the Great War. World War I introduced killing on an industrial scale, with new and gruesome ways devised to mow people down, poison them with toxic gas, and rain death down on them from above.

The horror of the fighting and the expansion of death and destruction into the civilian population caused many to call World War I “the War to End All Wars.” But, as one can see by the use of the Roman numeral, World War I did not close the book on global conflict.

Today, we are faced with numerous regional conflicts—such the Islamic State in Iraq and Syria and the Russian incursion in Ukraine—that are just waiting for some spark, like the couple assassinated a century ago, to turn them into the next world war.

Let us hope that that spark never comes. Or, if it does, that the nations involved can work together to pull themselves back from the brink.