Answer :
Final answer:
The Crusades were primarily caused by the holy crusade proclamation in 1095, leading to conflict between Christians and Muslims with lasting effects, and introduced new goods and knowledge to Western Europe.
Explanation:
The most significant cause of the Crusades was the proclamation of a holy crusade by Pope Urban II in 1095, with the goal of regaining control of the Holy Land from Islamic rule.
This religious motivation was fueled by the desire to reunite Christianity and strengthen the Byzantine Empire but resulted in lasting conflict and bitterness between Christians and Muslims.
During the Crusades, European knights brought back new goods and knowledge from the East, contributing to the spread of information and economic growth in Western Europe.