The Treaty of Rouen and the Outbreak of War Between Henry and His Brothers (1091)

In early 1091, William Rufus invaded Normandy with a large army, forcing Robert Curthose into negotiations. The two brothers, recognizing the need to strengthen their positions, signed a treaty at Rouen, which significantly altered the balance of power in Normandy and England—but at Henry’s expense.

With Henry excluded from the succession and now at odds with both brothers, war broke out between Henry and William Rufus & Robert Curthose.

The Treaty of Rouen (1091): Terms and Consequences

1. William Rufus gains Norman lands and castles

   • Robert ceded several key castles and territories in Normandy to William, strengthening his foothold on the continent.

2. William Rufus agrees to help Robert reclaim Maine

   • William promised military aid to Robert in reconquering Maine, which had broken away from Norman control in 1089.

3. Both brothers exclude Henry from succession

   • William and Robert nominated each other as heirs to both England and Normandy, ensuring Henry would inherit nothing while either one of them lived.

4. Robert and William agree to remove Henry from power

   • The treaty included a joint effort to take back Henry’s lands in western Normandy, specifically the Cotentin, where Henry had built a loyal power base.

The War Between Henry and His Brothers (1091)

• Now formally cut out of the succession, Henry became a direct enemy of both William Rufus and Robert.
• The brothers turned their forces against Henry, determined to strip him of his holdings and force him into exile.
• Henry, despite being outnumbered, was a skilled strategist, and this conflict would mark the beginning of his long and patient struggle for power.

Consequences and the Shifting Balance of Power

• The Treaty of Rouen (1091) strengthened William Rufus’ hold over Normandy, increasing his influence in northern France.
• Robert remained weak, relying on William’s support, while Henry was now a landless noble, forced to fight for survival.
• This war set the stage for the eventual showdown between the three brothers, ultimately leading to Henry’s eventual rise to power as King of England and Duke of Normandy.

The war that followed the Treaty of Rouen was the defining conflict of Henry’s early career, as he fought to reclaim his position and eventually surpass both of his brothers.