Final answer:
Pope Alexander III strengthened papal authority and clashed with Emperor Frederick I Barbarossa in 1163.
Step-by-step explanation:
In 1163, Pope Alexander III made significant strides in strengthening the papal authority and expanding the influence of the Roman Catholic Church. One of his notable actions was issuing the Papal Bull "Licet de vitandâ" which prohibited unauthorized appeals to the papal court, reinforcing the pope's jurisdiction as the final authority in church matters.
Alexander III also faced conflict with Emperor Frederick I Barbarossa, who sought to assert imperial control over the church. The pope excommunicated Frederick in 1160, a move that led to a long-standing power struggle between the papacy and the Holy Roman Empire.