The later kings of Ur appear to have retained possession of the empire acquired by Dungi, but we may assume that, like him, they were constantly obliged to enforce their authority. Tablets have been found at Susa dated by the official formulæ of Bûr-Sin,[31] proving that the capital of Elam remained under his control, but, before he had been two years upon the throne, he was obliged to undertake the reconquest of Urbillu. Other successful expeditions were made in his sixth and seventh years, which resulted in the subjugation of Shashru and Khukhunuri, or Khukhnuri. The date-formulæ of Gimil-Sin's reign record that he conquered Simanu in his third year, and four years later the land of Zabshali, while the only conquest of Ibi-Sin of which we possess a record is that of Simuru. A date-formula of this period also commemorates the marriage of the patesi of Zabshali to Tukîn-khatti-migrisha, the daughter of the king, but it is not certain to which reign this event should be assigned. Evidence of the extent of Gimil-Sin's authority in the direction of the Mediterranean may be seen in the date-formula for his fourth year, which commemorates his building of the Wall, or Fortification, of the West, entitled Murîk-Tidnim. Since Tidnu was explained by the Assyrian geographers as another name for Amurru[32] and may be connected with Tidanu, the mountain in Amurru from which Gudea obtained his marble,[33] we may infer that at least a portion of Syria acknowledged the suzerainty of Ur during his reign.