Final answer:
The crusaders, mainly French knights, entered Jerusalem in 1099 and committed a massacre of the local Muslim and Jewish residents. Over time, the Crusader States were established but were eventually contested by Muslim leaders, with Saladin taking back Jerusalem in 1187. The subsequent Third Crusade failed to recapture Jerusalem, leading to a treaty that allowed Christian pilgrims to visit the city.
Step-by-step explanation:
The crusaders entered Jerusalem in the summer of 1099. The opposition they faced was a mixture of local Muslim forces and later on, more organized resistance from Muslim leaders such as the Seljuks and the famous Sultan Saladin. Upon capturing Jerusalem, the crusaders committed a massacre, killing many of the Muslim and Jewish inhabitants, an event that caused horror among both faiths. Subsequently, the crusaders established the Crusader States, including the Kingdom of Jerusalem, to consolidate their hold on the region. Unfortunately, the tension and conflict between different factions persisted, leading to further struggles and crusades over the control of the Holy Land.
In 1187, Saladin successfully retook Jerusalem, causing a European reaction that spurred yet another crusade, this time lead by figures such as Richard the Lionheart. The Third Crusade, while managing to secure some victories, ultimately ended with a treaty that left Jerusalem under Muslim control but allowed for Christian pilgrims to visit the city. The presence of the crusaders in the region would continue until their last stronghold, Acre, fell in 1291.