 Later that year the Fourth Council of the Lateran opened.Upon his return from the council in 1216, Arnaud Amalric tried to convince Aimery and the citizens of Narbonne to renounce their submission to Simon, but the duke of Narbonne was at the height of his power and the viscount and citizens renewed their submission and were put under Simon's protection.In May 1217, Simon de Montfort was forced to besiege Toulouse after it had fallen into the hands of the deposed Count Raymond VI.