Final answer:
Western Europeans enthusiastically joined the First Crusade called by Pope Urban II for religious, ideological, and economic reasons, leading to the iconic act of marking their clothing with crosses, and directly impacting trade and political situations of the time.
Step-by-step explanation:
Response to Pope Urban's Call to Arms
Western Europeans responded to Pope Urban II's call to arms with fervor and commitment. After his proclamation at the Council of Clermont in 1095, soldiers, knights, peasants, and zealots alike felt moved by the concept of an armed pilgrimage to liberate the Holy Land. Lured by religious zeal, the promise of spiritual rewards, and possibly the prospects of adventure and wealth, many stitched crosses onto their clothing as a symbol of their commitment to the crusade, which is the origin of the term 'crusade'.
Religiously motivated warfare was a powerful concept that resonated across both Christianity and Islam, and the First Crusade exemplified such a conflict. These ideological underpinnings, coupled with geopolitical interests and the potential to redirect the energies of the warring nobility away from internal conflicts, were key factors driving the crusade's popularity.
Western Christians were driven by various reasons to join the crusades. Aside from the primary religious motive to support Christians in the Middle East, they also sought to reclaim sacred lands, especially Jerusalem. Furthermore, Venice and Genoa played a strategic role as their trade interests were affected by Ottoman control over eastern Mediterranean trade routes. The response included welcoming Ottoman defense of trade routes or calls for crusades to address military and trade concerns.