Urban II, originally named Odo of Lagery, was elected the 159th Pope of the Catholic Church in 1088 during a period marked by significant political turbulence and reform within the Church. His election was the result of a complex interplay of noble support and church interests, signaling a shift towards a more robust papal authority. Upon assuming the papacy, Urban II sought to address various issues plaguing the Church, including the moral integrity of the clergy and the ongoing conflicts in the Holy Land. His initiatives aimed to restore the Church's stature and unify Christendom under papal leadership.

One of Urban II's most enduring legacies was his call for the First Crusade, which he initiated at the Council of Clermont in 1095. This momentous assembly gathered thousands of knights and common believers, where Urban urged them to take up arms to reclaim Jerusalem, promising spiritual rewards and absolution of sins. His impassioned speech ignited the fervor of the faithful, leading to the mobilization of various armies predominantly from Western Europe, marking a significant religious and military undertaking.

Urban's influence extended beyond just the initial call for the Crusade; he played a vital role in shaping the moral and spiritual motivations of the crusaders, framing their mission as one of religious duty and valor. His papacy not only catalyzed military action but also set a precedent for papal intervention in secular matters, highlighting the intertwining of faith and political power. Urban's vision of a united Christendom engaged in a holy war would have lasting implications for European society and its relationship with the Muslim world for centuries to come.