I've been reading up on the First Crusade recently, and I began to realize why it was the most successful Crusade.
As a general rule, all the crusades have suffered because of infighting, poor supply lines, alienation of the Byzantines and the fact that so few European soldiers made it to the Holy Land at all.
The first crusade suffered all these problems. The reason it succeeded where the others failed is that the surrounding muslim powers were incredibly weak. The Seljuks were divided. The Fatimid Caliphate was in its death throes.
So, that got me thinking. What if the First Crusade was even more successful?
Firstly, the People's Crusade needs to not happen. That should be relatively easy. Simply kill off Peter the Hermit, and have Walter Sans Avoir and the other knights who joined the People's Crusade enlist in the later Princes Crusade.
This means that when the enlarged Princes Crusade reached Constantinople, they're met with open arms. (Bohemond's presence be damned) The Byzantines readily feed the Crusader army.
Alexios, since he isn't put off by the People's Crusade, gives full Byzantine support for the Crusade. This means that conquered territories will become part of the Byzantine Empire, and the sizeable Byzantine Army will join the Crusade.
As in OTL, the Sultanate of Rum is smashed. Anatolia is reclaimed for Christiandom. Unlike in OTL, they are adequately provisioned in their journey to Armenia and have larger Byzantine forces assisting them.
Baldwin becomes the count of Edessa, which remains a Byzantine vassal.
At Antioch, the Saxons arrive to assist the Crusade. Antioch is still a formidable obstacle; the greater provisions and troops however mean the Crusader army emerges from the siege in a better state than it had been. The city would have been starved out, but like OTL the armies of Mosul come to break the siege, a traitor opens the gates, and the Crusaders take the city.
Mosul's army is then, as in OTL, completely defeated. Here's the single largest shift in the crusade. OTL, the crusaders paused in Antioch for a year to debate whether their oaths to the Byzantines, who had deserted the Crusade, still existed. TTL, the oaths clearly do. So, instead of waiting a year, the large, well-provisioned Crusade has some time on its hands.
The Crusaders thus proceed down the coast as OTL, after capturing Aleppo, and besiege Jerusalem. By this point, and after the long journey, even their improved supplies are stressed. The city is taken in 1098.
The Crusaders then continue south, as the Fatimids refuse to negotiate. They defeat them, but do not expand into Egypt due to the logistical difficulties (the Crusaders ships had been made into siege engines, and so could not be used.) The first Crusade thus ends and the crusaders are allowed to return home or remain in their captured territories as Byzantine vassals.
The Byzantines however are stronger now. Mosul and Damascus can be invaded by them and whatever forces remained in the next few decades, restoring the Byzantine Empire outside of Egypt. It's even possible that they could attack the decaying Fatimid Caliphate and retake Egypt, once breadbasket of the Empire and home to large Christian populations.
What do you think?