(Above) A Templar Knight holding his flag
Causes and sides of the Fourth Crusade
The biggest side of the Fourth Crusade was the Crusader army put together by many of the kingdoms of Europe. Pope Innocent III was the "leader" of this side and he was the one who caused the war, when he decided that he wanted to capture Jerusalem.
The Israelites who were ruling Jerusalem probably had no idea what was going on northwest of them. Wether they did or did not know the Popes plans is unclear, but it is clear that they had no effect on the Fourth Crusade physically.
Venice was allied with the Crusader army, and they wanted to get a profit out of helping the crusaders. The didn't end up helping in the original plan, but when the crusaders put Alexus Comnenus on the thrown of Constantinople, and when they sacked Constantinople, the Venetians helped.
The last side was the Byzantine Empire in the form of the people in Constantinople. Originally they opposed Alexus Comnenus from being put in power again, and ended up assassinating him because of taxes. They tried to fight off the Venetians and the Crusaders, but were eventually sacked. Shortly after the sacking of Constantinople the Byzantine Empire fell.
The Israelites who were ruling Jerusalem probably had no idea what was going on northwest of them. Wether they did or did not know the Popes plans is unclear, but it is clear that they had no effect on the Fourth Crusade physically.
Venice was allied with the Crusader army, and they wanted to get a profit out of helping the crusaders. The didn't end up helping in the original plan, but when the crusaders put Alexus Comnenus on the thrown of Constantinople, and when they sacked Constantinople, the Venetians helped.
The last side was the Byzantine Empire in the form of the people in Constantinople. Originally they opposed Alexus Comnenus from being put in power again, and ended up assassinating him because of taxes. They tried to fight off the Venetians and the Crusaders, but were eventually sacked. Shortly after the sacking of Constantinople the Byzantine Empire fell.