Battle of Mortemer

The Battle of Mortemer was a defeat for Henry I of France when he led an army against his vassal, William the Bastard, Duke of Normandy in 1054. William was eventually to become known as William the Conqueror after his successful invasion and conquest of England.

William the Bastard became Duke of Normandy as a boy. His reign did not start well, and he had to experience twenty years of internal strife. The chronicler William of Jumièges reported that the duke's guardian, his teacher and his steward were all killed by rebels. Members of William's extended family attempted to unseat him. In 1046 there was a rebellion led by Guy of Burgundy, William's cousin. William defeated the rebels at the Battle of Val-ès-Dunes in 1047, with the support of Henry I of France.

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