the mill of Barbillon as the river carried them downstream en masse. The battle is traditionally said to have taken place on 10 August, but there is no decisive evidence for this date. The historian David Douglas argues for a date early in 1047 on the ground that the drowning of the fleeing army indicates that the Orne was flooded, which points to the winter or spring. However, David Bates dismisses this argument as the tidal nature of the Orne would account for the drownings. In his view, the battle almost certainly took place in the summer. Aftermath While the royal army drove much of the rebel army to the west, Gui of Burgundy and his surviving forces escaped to his lands in the east and holed up in the strategic castle of Brionne. Despite an energetic siege, William was not able to force the castle into surrender until 1050, and, during that time, he was not able to assert his authority in the eastern third of his duchy, which lay beyond Brionne. After the Battle of Val-ès-Dunes, there was still strong opposition to William among the Norman nobles, but they were forced to declare a "Truce of God" at Caen in October 1047. This truce, backed by the full endorsement of the Church, stated that private wars or vendettas were prohibited from Wednesday evening to Monday morning. The truce gave William special rights to defend his title and the public order; he did not, along with King Henry I, have to abide by the order. Even though William's position was still weak, with Gui of Burgundy still holding out and William having to pardon many of the barons who had opposed him, it would be five years before he had to face another major revolt. References Sources 1040s in France 1047 in Europe Battles involving France Battles involving the Normans Calvados (department) Conflicts in 1047 Duchy of Normandy William the Conqueror