Imad ad-Din Zengi
Baldwin II died on 21 August 1131. In accordance with his last will, Fulk and Melisende were jointly crowned on 14 September, but Fulk wanted to secure the government for himself and to reduce his wife to background. He replaced the castellans of the royal castles with his own retainers from Anjou and marginalized Baldwin II's most barons. In contrast with them, William retained the office of constable during Fulk's reign. He witnessed Fulk's three authentic charters as the first of the secular barons. The king confirmed Willim's donation to the canons of the Church of the Holy Sepulchre in 1132. William accompanied Fulk during his unsuccessful campaign against Imad ad-Din Zengi, Atabeg of Mosul, who had laid siege to Montferrand (at present-day Baarin in Syria) in July 1137.