But if we have little knowledge of the Lakhmid ḥîrahs which were the precursors of Ukhaiḍir on the eastern frontiers of the desert, we have another and a richer source of information in the Sasanian palaces. The Lakhmid princes stood in close relations with the Sasanian empire. Among the officials of the Persian court there was an Arab secretary whose special duty it was to conduct the correspondence with ‘the land of the Arabs’. Moreover, it is related that the Arab phylarch paid a yearly visit to the court of the Chosroës.[74] To a Lakhmid the education of a Persian prince was entrusted, and Lakhmid armies placed Bahrâm V upon a contested throne. The Christians of Ḥîrah belonged to the Nestorian church, the church of Assyria; we hear of one, the poet ‘Adi ibn Zaid, who was Arab secretary and enjoyed great influence with Khusrau Parwêz. Half allies, half vassals, the Lakhmid phylarchs fought side by side with the Persians against Rome;[75] they were sufficiently independent to receive an embassy from the Byzantine emperor, and sufficiently important to warrant an attempt on his part to buy them over from the Sasanians. Finally, at the beginning of the seventh century, Khusrau Parwêz set the Lakhmid dynasty aside and established in place of Nu’mân III an Arab of the Ṭayy, who lived and held his court at ‘Ain al-Tamr near Ukhaiḍir. Possibly the huge walls of Qaṣr Sham’ûn, on the outskirts of the oasis,[76] may date from the time when ‘Ain al-Tamr was the residence of the phylarch. But he was no longer an independent ruler; a Persian adviser was appointed to assist him, and a few years later the state was converted into a province of the Sasanian empire under a Persian regent. Independent or subject, the civilization of Ḥîrah must have been modelled upon that of Ctesiphon; Persian influence must have been predominant in its arts and its architecture, and the Lakhmid ḥîrahs must have reflected the glories of Sasanian palaces. It is to these palaces that we should look first for an explanation of the architectural scheme of Ukhaiḍir. One reservation must, however, be made. It is true that Ukhaiḍir cannot be regarded as primarily a fortress. The absence of any sufficient provision of water would have been a fatal weakness in time of siege. No cistern exists within the palace; no ancient well has been found, and if the conditions were the same of old as they are now (which is, however, by no means a safe assumption), any water within the palace would have been too brackish to drink, as is the case in the modern well in the palace yard. Moreover, the outer ring of walls, which encloses the northern annex, was obviously too weak for defence; it is more like the garden wall of a pleasure-ground. Nevertheless, considerable care has been lavished upon the defences of the main building. They were, and they are to this day, adequate for the spasmodic warfare of the Arab tribes. In the very act