He became count of Anjou (as Fulk V) in 1109. He was originally an opponent of Henry I of England and a supporter of Louis VI of France, but in 1127 he allied with Henry when Henry arranged for his daughter Matilda to marry Fulk's son Geoffrey Plantagenet.
Fulk visited the Holy Land in 1120, and become a close friend of the Templars. After his return he began to subsidize the Templars and also maintained two knights in the Holy Land for a year. In 1128 he was preparing to return to the East when he received an embassy from King Baldwin II of Jerusalem who had no male heir to succeed him. Baldwin arranged for Fulk to marry his daughter Melisende, which would allow Fulk to succeed Baldwin as king. Fulk accepted the offer and in 1129 he and Melisende were married, with the towns of Acre and Tyre as her dowry.
In 1131 Fulk became king of Jerusalem when Baldwin II died. The kingdom under Fulk was prosperous, and at the beginning of his reign he also acted as regent of the Principality of Antioch. As regent he had Raymund of Poitou marry the infant Constance, daughter of Bohemund II of Antioch. However, the greatest concern during Fulk's reign was the rise of atabeg Zengi of Mosul.
In 1137 Fulk was defeated near Barin. Fulk then allied with the vizier of Damascus, who was also threatened by Zengi, and was able to capture the fort of Banias, to the north of Lake Tiberias. Fulk also strengthened the kingdom to the south. His butler Paganus built the fortress of Kerak to the south of the Dead Sea, and to help give the kingdom access to the Red Sea, Fulk had Blanche Garde and other forts built in the south-west to overpower the Egyptian fortress at Ascalon.
In 1137 and 1142, Byzantine emperor John II Comnenus arrived in Syria attempting to impose Byzantine control over the Crusader States. John's arrival was ignored by Fulk, who declined an invitation to meet John in Jerusalem. Fulk died in 1143, leaving two sons who both became kings, as Baldwin III and Amalric I.
William of Tyre described Fulk as a capable soldier and politician, who defended both the kingdom and the church, reflecting the policies of his predecessors Baldwin I and Baldwin II. William felt that the major fault of Fulk's reign was his inattention to the defense of the states to the north against the invasions of Zengi, which culminated in the fall of the County of Edessa in 1143.
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Melisende (regent to 1152)