I hope you are talking about the Treaty of Verdun that was signed in the month of August of the year 843. It was one of the first treaties that divided the Carolingian Empire into three kingdoms among the three surviving sons of Louis the Pious. The Treaty of Verdun actually stopped the three year long Carolingian Civil War between the three sons. Each of the three sons of Luis the Pious had already established themselves in one of the Kingdoms. This made the signing of the treaty easier.
