The Old World looked quite a bit different in eleventh century than it does nowawdays. For one thing, there was the Byzantine Empire, a Christian nation which had lost a great deal of territory (including North Africa, Palestine, and Spain) to the Imayyid Caliphate. There were also a lot of Medieval peasants sitting around on their hands with nothing much to do. Pope Urban II was troubled by this fact, and so decided that something had to change. His solution? To launch a crusade against the Muslim world, and retake the stolen holy land of Jersualem.
It didn’t take long for the armies to be filled with young, idealistic soldiers, though this was mostly because the only other choice in those days was to be apprenticed to Cedric the Barrel Maker. They were soon divided into two camps: the People’s Crusade, which was made up of ordinary townfolk, and the Turks, who actually knew what they were doing. Neither side liked the other very much, but they still marched to Asia Minor together, where they discovered that it was quite a bit hotter there and that air conditioning hadn’t been invented yet.
The Crusaders were immediately met by harsh resistance from the Seljuk defenders. The vast majority of the People’s Crusade was massacred, though the main army remained intact. They started anew and attacked various cities, but consistently fell to the Muslim soldiers. Perhaps it was the unfamiliar territory, perhaps it was the difficulty with fighting an entrenched population, but for every man they managed to kill, they lost at least two in their place. Still, they were finally able recapture the city of Jerusalem, though they lost it again a short time later.
Since people are doomed to never learn from history, a second crusade followed in 1147, and then a third crusade in 1189, and a fourth in 1200, all the way to a ninth crusade in 1271. Each of these holy wars was the result of a powerful rally call from a charismatic leader and bloody desire to lop off some heads. Families would be torn apart, soldiers suffered from horrific injuries, though the trebechet industry did pretty good with the whole thing.