The Treaty of San Germano was signed on July 20, 1225 at San Germano, present day Cassino, between Holy Roman Emperor Frederick II and Pope Gregory IX. A Dominican named Guala was responsible for the negotiations.
Frederick promised 1000 knights over 2 years, transport for 2000 more knights and he would depart on Crusade in 1227 or lose 100,000 in gold or be excommunicated. He also promised that if he went on Crusade that he would lead.
After the treaty was signed, Guala became the bishop of Brescia. Based on the terms of the agreement, Frederick's forces ceased to occupy portions of the Pontifical States. Moreover, all papal possessions in Sicily were restored to the Pope.
References
Treaty of San Germano Wikipedia(Text) CC BY-SA