Hugh initially supported Stephen of Blois as king of England. On the death of Henry I in 1135, his nephew Stephen usurped the throne, despite the oath Stephen and the barons had sworn to accept Henry's daughter Empress Matilda as his successor. It was Bigod who asserted that, in his last days, Henry I had named Stephen to become king at the expense of his daughter Matilda. Civil war resulted when, in 1139, Matilda commanded the military strength necessary to challenge Stephen within his own realm.