 At the Council , Pope Gregory promulgated a new crusade in liaison with the Mongols , putting in place a vast program in his " Constitutions for the zeal of the faith " , with four main elements : imposing a new tax for three years , forbidding trade with the Sarazins ( Muslims ) , arranging the supply of ships by the Italian maritime republics , and the alliance of the West with both Byzantium and the Mongol Ilkhan Abaqa . Abaqa then sent another embassy , led by the Georgian Vassali brothers , to further notify Western leaders of military preparations . Gregory answered that his legates would accompany the crusade , and that they would be in charge of coordinating military operations with the Ilkhan . 
