History of the Crusades/The First Crusade

Launching the Crusade
The crusade was launched by Pope Urban II after he received a plea from the Eastern Roman Emperor, Alexios I Komnenos, who wished for military aid against the Seljuk Turks. The Seljuk Turks were Muslims who had occupied the Anatolian peninsula which had once been an integral province of the Eastern Roman Empire before it was lost following the Battle of Manzikert. In response, Pope Urban II convened the Council of Clermont in which the pope exhorted the Christians in the West, in particular the Frankish people, to come to the aid of their brethren in the East who the pope described as being under existential threat from the Muslims. The crusade was presented as an armed pilgrimage to Jerusalem in which those who took the cross to defend the people of Christ would obtain absolution for their sins.

There was a large outpouring of support for this enterprise as people from all social classes were inspired by the pope's call for action. While the nobles organized their military expedition, doing things like selling off their property in order to get the money needed to fund the journey to the East, the peasants were willing to strike out on their own. Following Peter the Hermit, the People's Crusade marched to the East but were massacred by the Turks. When the main body of the Crusaders organized by the nobility arrived in Constantinople, they pledged vows to the Emperor Alexios to return all they took from the Turks that once belonged to the Roman Empire.

The Battles of the Crusade
The first victory of the Crusade was at Nicaea where the crusaders laid siege to the capital of the Seljuk Sultanate of Rum while Kilij Arslan I was away. When the Sultan returned, he was defeated by the crusader army and Nicaea surrendered. As the crusaders marched across Anatolia, they were once more attacked by the Turks at the battle of Dorylaeum but once more the crusader army drove back the Turks. Finally, the crusaders arrived at Antioch and began the siege.

The crusaders were able to seize the city through treachery but then almost right after were besieged by Kerbogha, the Atabeg of Mosul. Conditions were dire as food was scarce and many of the crusaders died. Stephen of Blois deserted and upon encountering Emperor Alexios, told him that the situation was hopeless, causing the Emperor to turn back rather than relieve Antioch. After the crusaders supposedly found a fragment of the Holy Lance, they sallied out from the city and defeated Kerbogha's army. Antioch was in crusader hands, but due to what seemed to be a betrayal from Alexios, the crusaders refused to return Antioch to the Romans.

After the fall of Antioch, the crusaders faced little resistance as the marched toward Jerusalem as the towns in their path preferred to accommodate the crusaders rather than resist. Jerusalem was held by the Fatimids, an enemy of the Seljuks. Though the Fatimids wanted to ally with the crusaders to fight the Seljuks, the crusaders refused since their ultimate goal was Jerusalem. After a siege, Jerusalem was sacked by the crusaders. A Fatimid army led by vizier al-Afdal went to recapture Jerusalem, but they were defeated at the battle of Ascalon. After this, most of the crusaders returned home with only a few stayed behind to establish new states.

Establishment of the Crusader States
The County of Edessa was established before the siege of Jerusalem, when Baldwin left the main crusading army to Edessa to fight against the Muslims there. After the ruler of Edessa died, Baldwin married his daughter and took the title Count of Edessa.

The Principality of Antioch was established by Bohemond of Taranto who arranged the crusaders' capture of Antioch. He took the title Prince of Antioch and refused to subordinate himself to the Roman Emperor.

The County of Tripoli was established by Raymond of Toulouse.

The Kingdom of Jerusalem was the most important of the Crusader States. The first ruler of the Kingdom was Godfrey of Boullion, who didn't take the title of King but rather styled himself as the Advocate of the Church of the Holy Sepulchre. His successors were crowned as king instead, and attempts by ecclesiastical authority to take control over Jerusalem was thwarted.