Fifth Crusade (1 janv. 1217 – 1 janv. 1221)

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This, I think, is the most frustrating Crusade. I'm gonna go ahead and assume you've got a general idea of the goal here. So, naturally, the first step in taking Jerusalem would be to attack Egypt. Obviously, like, come on that's strategy 101. They actually succeeded in taking a port of Egypt and really freaking out the Muslims. They were offered not Jerusalem, not Edessa, but EVERY holy city.
If you're smart, you know what they did next.
They said no and lost their army at the Battle of Cairo.