Hi! I'm reading a book on the Crusades and am curious what would have happened if the First Crusade failed. Could the Byzantines have finished the job and revitalized the Empire?
In OTL, the crusaders left Constantinople and conquered Nicaea (returning it to Byzantine control because Alexius Comnenus had enforced the crusaders' oath of allegiance to him). They then proceeded to besiege Antioch. After a grueling siege, they break into the city only to be besieged in turn by a Turkish relief force. They were in dire straits and were very fortunate to keep the city. They had hoped to get reinforcements from Constantinople but none arrived (Alexius had thought about sending men but I believe he got the impression that it was too little too late).
ITTL, the Turks defeat the crusaders and retake Antioch. Shortly after they wipe out the last of the crusaders, Alexius (who had hoping the crusade would succeed and add more territory to the Empire) has his reinforcements besiege the Turkish relief force trapped in the city. The Turks are defeated (suffering the same fate as the crusaders ITTL and having even a lower chance of survival due to fatigue and the crusaders having left even fewer resources in the city) and Antioch is controlled...by Alexius.
With Nicaea and Antioch under his control, he finds himself in a position where he can finish the crusade and reconquer Jerusalem. Many of the Muslim towns between Antioch and Jerusalem were so scared of the invaders IOTL that they surrendered without a fight. The Byzantines face little resistance en route to Jerusalem (spreading rumors that their troops are going to be as barbaric and frightening as the lost crusader forces) and conquer the city. Pope Urban's mission seems to be a success in that the conquerer of Jerusalem is Christian...or is it?
What would all of the major leaders have thought of this situation?
ALEXIUS: He's got a strong presence in the Eastern Mediterranean. The Islamic kingdoms are in disarray, having been decimated by the crusaders. He may have some time to mop up what's left and reinforce his positions. He may very well be in a position to expand his empire.
URBAN: In for a big surprise! The crusade did what it was supposed to do in that it reinforced the Byzantines. He may have never expected for Jerusalem to be retaken by the West. But what does he do now? The head of the Catholic Church isn't going to let the Greek Orthodox get away with running Jerusalem, is he? Would he be content with a half-victory? There's no way he could declare a crusade against the Greek Orthodox because with the Muslims temporarily out of the way the Byzantines would demolish him.
VARIOUS HEADS OF EUROPEAN COUNTRIES: God ensures that Catholic soldiers fail to conquer Jerusalem (even with a possible holy relic in their midst). Yet the Greek Orthodox soldiers seem to not have a problem. Obviously, God prefers Greek Orthodoxy to Catholicism! Are conversions to Orthodoxy going to start taking place among Western Europe?
ISLAMIC LEADERS: You can imagine what they're thinking: "These infidels declared a holy war against us and took our third holiest city. Well, two can play at that game! We beat up on the Byzantines before, we'll do it again!"
I can almost imagine Alexius populating the area with lots of Greek Orthodox and daring the Pope to kick them out. Getting rid of crusader states is probably going to be a lot harder if they're more closely tied to Constantinople.