Final answer:
Pope Urban II called for the First Crusade to secure religious control and access to holy sites in the Holy Land. The Crusades aimed to liberate the Holy Land from non-Christian rulers and defend the Christians living there. While religious motives were prominent, the Crusades also had political and economic implications.
Step-by-step explanation:
Pope Urban II called for a military expedition to retake the Holy Land primarily for the purpose of securing religious control and access to holy sites. The Holy Land, which included Jerusalem and other significant sites for Christians, Jews, and Muslims, was held by Muslim rulers. The goal of the Crusades was to liberate the Holy Land from non-Christian rulers and defend the Christians living there. While the Crusades were initially focused on religious motives, they also later served political and economic purposes for the Church.