The First Crusade was a military expedition initiated by Western Christian nations aimed at reclaiming Jerusalem and the Holy Land from Muslim control. It commenced in 1096, following a call from Pope Urban II for Christians to take up arms. The Crusaders, comprised of knights and peasants, traveled across Europe, eventually capturing Jerusalem in 1099. This campaign marked a crucial moment in medieval history, leading to a series of subsequent Crusades. The First Crusade shaped Christian-Muslim relations and had lasting effects on politics, culture, and religious dynamics in the region for centuries to come.