WATCH: Impact of the crusades

- [Sal] We've already had several videos where we give an overview of the Crusades. And just as a review, they happen over roughly 200 years during the High Middle Ages. The first Crusade at very end of the 11th century and actually the most successful of the Crusades, allowing the Western European powers to take control of Jerusalem and much of the Holy Land. And you could see that here on this diagram where Jerusalem, at least, goes from green to red, controlled by the Western European, the Latin Christians. And they're able to maintain control through these Crusader kingdoms all the way until 1187, when Salah ad-Din is able to retake control of Jerusalem. Then a few decades later, as we go into the Sixth Crusade and the Barons' Crusade, which isn't depicted here, the Western Europeans are able to take more control but eventually, the Muslims take control of Jerusalem and as we enter into the 14th century, they have control of the entire Holy Land. Now while that is happening, Constantinople gets sacked at the end of the Fourth Crusade by the Crusaders themselves and even though it's retaken, this is really the beginning of the end for the Byzantine Empire. So let's think a little bit about how the Crusades changed Europe and the entire world. Well, one of the obvious impacts of the Crusades was just the amount of death it caused. It's estimated that the death toll from the Crusades is two to six million people just from Western Europe. And just to put that into perspective, the European population at the time was about 60 to 70 million folks. So we're talking about four to 10 percent of the population dying in the Crusades. And this isn't fully accounting for all of the death and destruction that happened on the way to the Crusades or that happened in the Middle East as well. If you look at this map of what the region looks like as we get into the 14th century, right over here, you can see that although the Middle East is still in control of the Muslims, Muslims have for the most part been pushed out of the Iberian Peninsula, and they have a little bit of a foothold right here in Grenada. And this Reconquista is going to continue all the way until 1492 when what will be the Spanish are able to push out all of the Muslims from the Iberian peninsula and as they do that, they also expel the Jews. You also have territorial gains in the north of Europe that's a little bit harder to see on this map over here. As I mentioned in previous video, part of this Crusader mentality was not just about taking land back for the Byzantines or taking land from the Muslims, but also trying to take land or convert what were perceived as pagans in the north, German tribes that had not as yet converted to Christianity. And so that helped for territorial expansion in the north of Europe. Now a big theme in the Crusades was the power of the Pope. Remember, the Crusades were started by a Pope working people up, saying, "Hey, let's go help the Byzantines. "Let's go take back land from the Muslims." Pope Urban II. And over the course of this 200 years, you have this religious fervor where the Pope is organizing these Crusades. People are feeling this religious spirit. Many people are, before going on their Crusade, they're bequeathing their land to the Church. If they die, and many of these lords do end up dying, they're giving their property to the Church, headed by the Pope. Kings also gained power during the Crusades. In other videos, we talk about the feudal system and many times the vassals to the kings, the dukes, the counts, the barons, often had more control over their territory than the kings might have had. And they were constantly squabbling with each other but as people started to focus their energies on this external adventure known as the Crusades, first of all, many of these lords died, their property went back to the state, went back to the kings. You start having less internal dissension. In a way, this idea that Pope Urban II thought of at the end of the 11th century. Hey, why don't I point people externally so they stop worrying about what's going on internally? It kind of worked. Another trend is the importance of cities. In the feudal system, it's all about these manors and all about these estates. But in order to finance the Crusades, centers of trade and commerce became more important and also, as there was more interaction between West and East and more people traveling, you can imagine that it fostered trade which centered at these cities. And that goes into the next point, commerce and trade itself was fostered by the Crusades. It wasn't all fighting. The Venetians and other trader city-states, they helped facilitate the movement of arms and people from West to East, but on the way back, they also brought goods to trade. And so they became much, much more powerful. In fact, by the end of the Crusades, as we get into the 14th century, Venice, which is right over here on our map, was considered the richest and most powerful city in Europe. Venice has all of this trader wealth and it's not just from trade. As you might remember from previous videos, when Constantinople was sacked, it was sacked in part by these Venetian traders and after that, they built an empire. They broke up the Byzantine empire and took some of it for themselves. And so it's not a coincidence that as we get into the 14th and 15th century, places like Venice and Florence, famously sponsored by the Medici family, a famous banking family. So once again, these are centers of trade, centers of commerce became the places where the Renaissance would first flourish. And last but not least, as in some ways bloody and dark a time as the Crusades were, they were also associated with learning because you had all of these people go from Western Europe to the Middle East and the Holy Land and at that time, remember, we have videos on the Golden Age of Islam. In a lot of ways, they were shepherding the knowledge of the Ancient Greeks and the Romans and they were merging that with knowledge from the Indians and the Chinese and also coming up with innovations on their own. And a lot of the Western Europeans brought that back to Europe.