[3] Ascalon was a threat to the kingdom during the first half of the 12th century; the Fatimids staged raids from the city in most years aimed at Jaffa and the surrounding country, while its strong defences and harbour made it impervious to crusader attack.
The construction of Ibelin and the other castles went some way to alleviate this situation, leading to a successful campaign in 1153 which saw the fall of Ascalon to the crusaders.
[3] The importance of Ibelin and the other forts declined in 1153 with the fall of Ascalon to a siege and assault by King Fulk and the crusader army, and by the building of fortifications further south at Gaza and at Darum.
Ibelin is reported to have been a square enclosure, with four towers, which is comparable to Castel Arnaldi, Beth Gibelin, and Blanchegarde, of which some ruins survive.
In 1141 king Fulk, the leading barons, the patriarch and the bishops, made a joint decision to build a castle north of Ascalon at Ibelin, their name for the town of Yibna.
The site was a tell to the east of the town, an artificial mound marking an ancient ruins of previous settlements stretching back to biblical times.