The point is that an aggressive, invasive warfare had been going on between Europeans and Islam for hundreds of years. Shortly before the First Crusade, the Normans drove the Muslims out of southern Italy and Sicily. But the Muslims were still in Spain. As a matter of fact, about thirty years before the First Crusade, the pope tried to get a Crusade going to Spain, which was about half-reclaimed at the time. And that presents an interesting contrast. Spain was close; you didn't have to march 2500 miles; and there were riches to be had in Spain. Yet nobody went. The reason nobody went, and then thirty years later they all went, if you will, is because nobody believed that Jesus had walked around in Spain.

It really was a religious Crusade. If you don't believe it, all you have to do is look at the mortgages, documented by Riley-Smith, where the people taking out the mortgages go on at length about why they're borrowing the money in order to go. It was about Jesus.

Cultures change. What is overlooked about the Crusaders, and the knights and nobility of the 10th century and thereabouts, is that they were very bloody-minded. They had been raised since infancy to devote themselves to fighting. They were very sinful. They particularly were into coveting wives. And they were very religious.

The fact that these things can be combined strikes the modern mind as bizarre. But you have to deal with it if you're going to understand these people. They would commit a horrid crime, and their confessor would say, "I don't know if you can ever get over that one. I don't know if atonement is in the books for you. But you better walk barefoot to the Holy Land and hope that that works."

And they'd go. And then come back and sin some more.

It takes some stretching to understand what motivated these people.

Popular media representations of the Crusades depict the white-skinned Europeans slaughtering and conquering the brown-skinned natives. Yet the picture is more complicated than this. You point to the fact that the Holy Land had previously been inhabited by many Christians and Jews. Were there still Christians and Jews living in the Holy Land when the Crusades began?

Sure. Probably the majority of the population in some parts of the Holy Land still were Christians and Jews. Certainly most of North Africa was still mostly populated by Christians and Jews as well. There were these small ruling Muslim groups on top; the conversion to Islam took centuries and centuries before Christians more or less disappeared. 

The civilization we typically associate with Islam was in fact the civilization of the Christians and Jews they were ruling. When those Christians and Jews finally disappeared, so too did that advanced "Muslim" civilization. Suddenly the Muslims were all backward, and the question was, "How did they lose all that civilization?" They didn't. They never had it.

The famous "Islamic" architecture, for example, was not Islamic. It was eastern Christian.

A Ridley Scott film, The Kingdom of God, presented Saladin as principled and restrained in his conduct of war, and the Europeans as utterly lawless and rapacious. Is this accurate?

No, not at all. Saladin was your typical eastern butcher. He liked to chop people's heads off personally. Somehow, in the late 19th century, people got into romanticizing Saladin as part of this genteel, sophisticated eastern culture.