Final answer:
Pope Urban II called for the First Crusade at the Council of Clermont in 1095 to aid the Byzantine Empire and liberate the Holy Land. The call was based on religious zeal and the desire to unite Christians and the Church. Urban was in France because of political strife with a rival pope in Rome.
Step-by-step explanation:
Pope Urban II called for the First Crusade in response to the Byzantine Empire's request for military aid against the Seljuk Turks.
The proclamation at the Council of Clermont in 1095 appealed to Christians to embark on an armed pilgrimage to liberate the Holy Land. Various motivations spurred the First Crusade, including religious zeal, a desire to aid fellow Christians, the appeal of adventure, and the hope of absolution from sins. The crusade was also seen as a way to unite the Christian world and to extend the influence of the Church.
Moreover, Urban II was not able to call for the crusade in Rome because the city was occupied by a rival pope, which was supported by the German emperor. This political strife influenced Urban's decision to rally Christians while in France. Urban's call was founded on the rhetoric of holy war and religious duty, which was a powerful motivator for Europeans of the time.