Innocent III
1160 - 1216
Pope Innocent III was a firm believer in the most extreme claims of the papacy and his pontificate marks the most powerful moment of Papal domination.

Innocent III was the guardian of the young Frederick II but soon became entangled in a power struggle after Frederick had secured the imperial crown.

Innocent presided over the Fourth Crusade and the crusade against the Albigensian heretics in France. He also gave approval to the works of St.Francis and St.Dominic, and convoked the 4th Lateran Council.

www link :

The Medieval Sourcebook:
Summons to a Crusade,1215