The Fourth Crusade is for me, in many ways, the Crusadiest of all the Crusades. Sure, the First Crusade actually achieved its goal, which you can’t really say about any of the others in any serious sense, and other Crusades produced quintessential Crusading heroes like Richard the Lionheart and Saint Louis. But overall the Crusades were, and again this is just my own view, an enterprise that was marked more by petty infighting, poor planning, and a tendency to shoot (or stab) oneself in the foot than by dashing heroes or the triumphant “recovery” of the Holy Land for Christ. And the Fourth Crusade has more of that first list of stuff than any of the others. Any major military campaign that sets out to battle Muslims in the Levant and instead brings down the longest-lived Christian kingdom in the world, in Greece, is worth special consideration in my book.
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The Foreign Exchanges Companion 
Couple of notes.
1) A lot of people in Eastern Europe are still sulking over this. Yes, in many cases that’s an artificial construct of 19th century nationalism or post-Communist religionationalist reorganization, bit it’s nevertheless a thing.
2) Enrico Dandolo was *90 years old* and *blind*. Nevertheless he was still of sound mind and a fierce, competent leader. During the thick of the fighting he demanded to be placed in the forepeak of the Venetian flagship, where he was subject to arrow and missile attack but also where the whole Venetian fleet could see him.
Weirdly, there is still a plaque for Dandolo in the Hagia Sofia, even though his remains are supposed to have been thrown into the Bosphorus long ago.
3) Yeah, Byzantium was already pretty sick and rotten. A small, hungry army without siege equipment captures the largest, most well fortified city in the world? That’s Pizarro level craziness, and it could only happen because the Byzantines were so corrupt and fissiparous.
4) The Sack led to that weird period when Venice and (especially) Genoa were masters of the Black Sea. Which in turn led to the Black Death spreading across Europe. The Plague probably would have hit Europe at some point anyway, but its arrival in 1348 was a historical accident that can be traced pretty directly back to the Fourth Crusade.
Doug M.