After the defeat of Alfonso VIII, King of Castile, at Alarcos, Kings Alfonso IX of Leon and Sancho VII of Navarre entered an alliance with the Almohads and invaded Castile in 1196. By the end of the year Sancho VII had dropped out of the war under Papal pressure. Early in 1197, at the request of Sancho I, King of Portugal, Pope Celestine III declared a crusade against Alfonso IX and released his subjects from their responsibilities to the king, declaring that "the men of his realm shall be absolved from their fidelity and his dominion by authority of the apostolic see." Together the Kings of Portugal, Castile, and Aragon invaded Leon. In the face of this onslaught combined with pressure from the Pope, Alfonso IX was finally forced to sue for peace in October 1197.