Who called on Christians to retake the holy land from the Muslim Turks?

Pope Urban II called on Christians to retake the Holy Land from the Muslim Turks. His exhortation marked the beginning of the First Crusade in 1095, where he urged European Christians to embark on a pilgrimage to reclaim Jerusalem and other sacred sites. This call was a response to the request for military assistance from the Byzantine Empire, which was facing Islamic expansion. The Crusade ultimately aimed to unite Christians and restore Christian control over the region.