...I truly believe that the First Crusade was comparable to World War I in the way that it introduced into Europe a new and extraordinary brutal styl… - Jay Rubenstein

This is one moral I am comfortable drawing: When the leaders who direct wars and the men who wield the weapons of war become convinced that their actions align perfectly with the divine, we are inviting unthinkable atrocities. It’s a big enough lesson that putting it into words verges on the maudlin. But, unfortunately, it’s a lesson that is relevant for our world.

One of the most memorable twelfth-century observations about the crusade was how comfortable the soldiers felt around corpses. Two writers say, essentially, the people naturally feel horror at the dead, but the crusaders learned to walk among them and even sleep beside them. How did that happen? How did a basic human impulse, that crosses the medieval-modern divide, become lost?

Were the crusades a clash of civilizations? In brief, yes. That at least is the answer that the crusaders would have given. And the idea didn't die with them. In the centuries following, historians, whether celebrating or condemning the crusades, whether seeing them born of faith or colonial greed, nonetheless discussed them in terms of Islam vs. Christianity and East vs. West.