William the Conqueror’s Final Campaign and Decline (1086–1087)

By late 1086, William the Conqueror had left England and returned to Normandy, where he continued his continental policies, including alliances against King Philip I of France. One of his final diplomatic moves was marrying his daughter, Constance, to Alan Fergant, Count of Brittany, strengthening ties between Normandy and Brittany. Meanwhile, his rebellious son, Robert Curthose, had been wandering Europe, allying with King Philipand stirring unrest, leading to William’s final military campaign in the French Vexin in 1087.

Robert Curthose’s Wanderings and Alliance with Philip I

• After Matilda’s death in 1083, Robert, who had frequently quarreled with his father, left court and traveled throughout France, Germany, and Flanders.
• He sought the hand of Matilda of Tuscany, one of the greatest heiresses of the age, but his suit was unsuccessful.
• During his time as a wandering knight, Robert fathered several illegitimate children and gained experience in military and political affairs.
• By 1087, Robert had returned north and, still allied with Philip I, began stirring up trouble for William in Norman borderlands.

William’s Response: The Campaign Against the French Vexin (July 1087)

• With Robert acting as a destabilizing force and King Philip I continuing to challenge Norman authority, William launched an expedition into the Vexin in July 1087.
• William’s forces laid waste to the region, culminating in the seizure of Mantes, a key strategic town.
• However, during the capture of Mantes, William either fell ill or suffered an injury, reportedly struck in the abdomen by the pommel of his saddle.

Consequences and the Beginning of William’s Final Days

• William’s illness or injury at Mantes marked the beginning of his final decline.
• The wounds and exhaustion from the campaign left William severely weakened, forcing him to withdraw from active command.
• His condition rapidly deteriorated, leading to his death in September 1087.

Legacy of William’s Final Actions

• The marriage of Constance to Alan Fergant reinforced Normandy’s alliance with Brittany, creating a counterbalance against France.
• Robert’s continued defiance and alliance with Philip I foreshadowed the ongoing Capetian-Norman struggles, which would last for generations.
• William’s final campaign in the French Vexin demonstrated his unyielding military ambition, even in his last years, but ultimately led to his death and the division of his realm.

The campaign against the French Vexin in 1087 was William’s last military action, and his fall at Mantes set the stage for his death and the struggles between his sons over his vast empire.

The Treaty of Mantes: Philip II and Richard’s Ministers Reach a Settlement (July 9, 1193)

As Philip II of France continued his campaign in Normandy during Richard I’s captivity, he made significant territorial gains. However, rather than pushing further, Philip agreed to negotiate with Richard’s ministers, leading to the Treaty of Mantes on July 9, 1193.

Terms of the Treaty of Mantes

1. Philip Retains His Conquests

   • The treaty recognized Philip’s territorial gains in Normandy, allowing him to keep the lands he had seized.

2. Further Concessions to Philip

   • In addition to his existing gains, Philip was granted extra territories, further expanding Capetian influence at the expense of the Angevin Empire.

3. Philip Agrees to Halt Aggression in Normandy

   • In exchange for these territorial benefits, Philip pledged to cease further attacks on Normandy, bringing temporary stability to the region.

4. The Conditional Return of Captured Lands

   • Philip agreed to hand back captured lands to Richard under one condition—
   • Richard must pay homage to Philip, recognizing him as his overlord for his lands in France.

Significance of the Treaty

• Philip capitalized on Richard’s absence, expanding his territory without having to engage in prolonged warfare.
• The condition requiring Richard’s homage reinforced Philip’s position as the feudal overlord of the Angevin lands, a longstanding Capetian ambition.
• The agreement bought Philip time to consolidate his new holdings while awaiting Richard’s release from captivity.

Despite its temporary nature, the Treaty of Mantes strengthened Philip’s position in France, furthering his strategy of weakening Angevin control while positioning himself as the dominant ruler in Western Europe.

The Death of Philip II and the Accession of Louis VIII (July 14, 1223)

On July 14, 1223, King Philip II of France died at the age of 58, marking the end of a transformative reign that had solidified Capetian power and greatly expanded the French kingdom. His son, Louis VIII, immediately succeeded him as King of France, continuing his father's efforts to strengthen royal authority and diminish English and feudal influence in France.

Philip II’s Legacy

• The First King to Style Himself as "King of France"

  • Philip was the first Capetian ruler to officially use the title "King of France" (Rex Franciae), rather than "King of the Franks", reinforcing the idea of a centralized, national monarchy.

• Territorial Expansion

  • His victory at the Battle of Bouvines (1214) secured Normandy, Anjou, Maine, Touraine, and Poitoufrom the English Plantagenets, permanently weakening English claims in France.
  • His wars with John of England led to the collapse of the Angevin Empire on the continent.

• Administrative and Legal Reforms

  • Philip strengthened royal administration, centralizing power through a more efficient bureaucracy.
  • He expanded the use of royal officials (baillis and prévôts) to manage territories directly under the Crown, reducing feudal autonomy.

• Military Innovations

  • Philip organized a semi-permanent royal army, shifting France away from reliance on feudal levies.
  • He was one of the first European rulers to use infantry effectively, as demonstrated at Bouvines.

• Urban and Economic Growth

  • He revitalized Paris, improving its fortifications, roads, markets, and bridges, helping it emerge as a true capital city.
  • He introduced monetary reforms, stabilizing the French economy and reducing noble resistance to royal taxation.

The Accession of Louis VIII

• Philip was succeeded without dispute by his son, Louis VIII, who had already acted as regent and led military campaigns, including the Capetian invasion of England in 1216–1217.
• Louis VIII would continue his father’s policies, particularly against the English in Aquitaine and the remnants of the Albigensian resistance in the south.

Philip II’s death in 1223 marked the end of an era, but his reign laid the foundations for France’s rise as the dominant power in medieval Europe. His conquests, reforms, and military successes ensured that the Capetian monarchy would continue to grow in strength under his successors.