Final answer:
The First Crusade was called by Pope Urban II and was motivated by the control of Jerusalem by Muslim Turks, an appeal for help from the Byzantine emperor, and the idea of reclaiming the Holy Land for Christianity. The religiously motivated warfare played a significant role, as did the desire for spiritual salvation among western Christians.
Step-by-step explanation:
Causes of the First Crusade
The First Crusade, called by Pope Urban II, had several major causes that contributed to the western Christians’ decision to embark to the Middle East. One significant cause was that the Muslim Turks controlled Jerusalem, a city sacred to Christianity. Additionally, the Byzantine emperor Alexios I appealed to the pope for assistance, contributing to the pope's call to action.
While Pope Urban II wanted to reclaim the Holy Land from Muslim control for religious reasons, the emperor hoped for military support against the Seljuk Turks. The Byzantines did not ask Pope Leo III for help; it was Pope Urban II who issued the call for the First Crusade. The idea of religiously motivated warfare in Christianity and Islam played a significant role in the launch of the crusade, as the pope framed the conflict between Byzantine and Seljuk as a fight between religions.
Western Christians were compelled by several motivations, such as spiritual salvation, to join the Crusades. They saw Jerusalem as the most sacred of relics, a gateway to heaven itself, which motivated many to travel and 'liberate' it. The concept of the crusade also extended to other fronts such as Spain and the Baltic region, where the Christian forces fought against the Muslims and other non-Christians integrating the crusading rhetoric into the political goals of kings and monarchs.