How did William I strengthen his control over Normandy?

To strengthen his control over Normandy, William I employed several strategic administrative and military measures:

• Consolidation of Authority: He replaced disloyal nobles and ducal servants with his own trusted friends and supporters. He also limited private warfare among his vassals and recovered ducal rights that had been usurped by others.
• Defining Vassalage: He clearly defined the duties of his vassals, ensuring a more structured and loyal feudal hierarchy.
• Military Success: William suppressed internal revolts and decisively defeated external threats, such as the forces of King Henry I of France and Geoffrey Martel, count of Anjou, at the battles of Mortemer (1054) and Varaville (1057).
• Territorial Expansion: By conquering Maine in 1063, he established himself as the most powerful ruler in northern France.
• Strategic Alliances: His marriage to Matilda of Flanders secured a vital alliance with Flanders, which helped stabilize his position and provided support for his broader political ambitions.