Norman Conquest Encyclopedia
The Battle of Mortemer was the first set-back suffered by Henry I of France when he, together with the Count of Anjou invaded Norman territory from the north in 1054. His vassal, William the Bastard, Duke of Normandy, had become too powerful for Henry's comfort, a complete reversal of the situation in 1047 when he had supported William's cause at Val-ès-Dunes. Robert, count of Eu, seized the advantage offered by the king's commanders Odo, count of Blois and Rainald, count of Clermont when they permitted widespread pillaging by their men. The invaders were picked off piecemeal near Mortemer and the incursion collapsed without William's having to do much at all.