attempt was made to seize William at Valognes, but he escaped under cover of darkness, seeking refuge with King Henry. In early 1047 Henry and William returned to Normandy and were victorious at the Battle of Val-ès-Dunes near Caen, although few details of the actual fighting are recorded. William of Poitiers claimed that the battle was won mainly through William's efforts, but earlier accounts claim that King Henry's men and leadership also played an important part. William assumed power in Normandy, and shortly after the battle promulgated the Truce of God throughout his duchy, in an effort to limit warfare and violence by restricting the days of the year on which fighting was permitted. Although the Battle of Val-ès-Dunes marked a turning point in William's control of the duchy, it was not the end of his struggle to gain the upper hand over the nobility. The period from 1047 to 1054 saw almost continuous warfare, with lesser crises continuing until 1060. Consolidation of power William's next efforts were against Guy of Burgundy, who retreated to his castle at Brionne, which William besieged. After a long effort, the duke succeeded in exiling Guy in 1050. To address the growing power of the Count of Anjou, Geoffrey Martel, William joined with King Henry in a campaign against him, the last known cooperation between the two. They succeeded in capturing an Angevin fortress but accomplished little else. Geoffrey attempted to expand his authority into the county of Maine, especially after the death of Hugh IV of Maine in 1051. Central to the control of Maine were the holdings of the Bellême family, who held Bellême on the border of Maine and Normandy, as well as the fortresses at Alençon and Domfront. Bellême's overlord was the king of France, but Domfront was under the overlordship of Geoffrey Martel and Duke William was Alençon's overlord. The Bellême family, whose lands were quite strategically placed between their three different overlords, were able to play each of them against the other and secure virtual independence for themselves. On the death of Hugh of Maine, Geoffrey Martel occupied Maine in a move contested by William and King Henry; eventually, they succeeded in driving Geoffrey from the county, and in the process, William had been able to secure the Bellême family strongholds at Alençon and Domfront for himself. He was thus able to assert his overlordship over the Bellême