How did Pope Innocent III change the power of the medieval papacy?

Pope Innocent III significantly transformed the medieval papacy by establishing a powerful doctrine of papal monarchy, asserting that the pope acted as the representative of God on Earth. He expanded papal authority in both spiritual and secular spheres through several key actions:1

• Centralization of Church Power: Innocent reformed the Roman Curia and reorganized the judicial system, strengthening the church's hierarchical structure. He mandated the subordination of bishops to the pope, requiring papal approval for episcopal translations, resignations, and depositions.1
• Secular Influence: He famously used the metaphor of the Sun and the Moon to argue that royal power derived its dignity from papal authority. He intervened in the marital affairs of princes and established the right to evaluate imperial candidates in contested elections, a claim formalized in canon law.1
• Territorial Expansion: He reestablished and expanded the pope's temporal authority over the Papal States, effectively functioning as a secular prince in central Italy.21
• Crusades and Heresy: Innocent pioneered the use of the Crusades to combat internal papal enemies and heretics, such as the Albigensian Crusade, treating heresy as treason against God.1