In 1128 Fulk's son Geoffrey Plantagenet married Matilda, dowager Empress and Henry I of England's daughter. To her Henry had promised the succession of England and Normandy. But on Henry I's death in 1135 Stephen of Blois, Henry's nephew and favourite, seized the kingdom and the duchy.

The counte of Blois had long been rivals of the Angevins whose lands abuttedk theirs; their possessions almost encircled the French royal domain. The two halves, Blois and Champagne, were several times divided between heirs. When Hugh, count of Champagne, became a Templar in 1125, his county went to his nephew Theobald II of Blois, the grandson of William the Conqueror, king of England and duke of Normandy.

Theobald's brothers, Stephen count of Mortain and Henry bishop of Winchester, had earned the trust and patronage of their uncle Henry I of England.

In 1135 they together made sure that Stephen rather than Theobald took Henry I's lands.

In 1136, 1137, and 1138 Geoffrey and Matilda mounted campaigns in Normandy. With the help of Robert earl of Gloucester, a leading Anglo-Norman noble, Matilda invaded the kingdom of England in 1139, leaving Geoffrey to conquer the duchy. By April 1141 Geoffrey had taken control of much of Western Normandy. In 1144 he took Rouen and was invested as duke. In 1145 Arques, the last of Stephen's strongholds, fell to him. Insurrections in Maine and Anjou occupied the next few years, during which time his son Henry emerges as Matilda, his mother's champion, and untimately as heir to her claims.