The reason for the crusades was to take back Jerusalem and to spread religon.
The first crusade Israel controlled by Muslim leaders who allowed Christians to make a pilgrimage to Jerusalem. 1071 Seljuk Turks take over Jerusalem and march on Constantinoble. The emperor of the Bysantine Empire asks the Pope for help. Pope Urban the second called for a crusade to take back Jerusalem.
The crusaders attacked Constantinoble for three days smashed Christian icons, stole relics and attacked women.
1144 Second crusade muslims counter attack and conquer Edessa
The third crusade organized by rulers of England, France, and Germany (the crusade of kings). Richard the first of England(the lion heart). Saladin and Lionheart sign a truce to end the third crusade.
Truce to end crusade
The fourth crusade was a fail for the pope who launched the crusade
Byzantines never forgave catholic Christians.
Crusades brought western Europeans into contact with Byzantines and Muslims. Western Europeans gained new knowledge architecture (domes), mosaies, build better ships, make more accurate maps use of a compass to tell direction. Wealthy Western Europeans began to want eastern goods such as spices, sugar, silk, and lemons.