Thanks to the intuition of the discordant oligarchs of an oasis-state in the Hijāz, who had invited the rejected prophet of a rival community to make himself at home with them and try his hand at being their ruler, in the hope that he would bring them the concord which they had failed to attain by themselves, Yathrib became, within thirty years of the Hijrah, the capital of an empire embracing not only the former Roman dominions in Syria and Egypt but the entire domain of the former Sasanian Empire. [Footnote: Ibn Khaldūn suggests that the Primitive Muslim Arabs’ success in conquering the whole of the Sasanian Empire was a consequence of their conquest of the Sasanian imperial capital Ctesiphon, and that their contemporary failure to conquer more than a portion of the Roman Empire was a consequence of their inability to conquer the Roman imperial capital Constantinople (see the Muqaddamāt, translated by de Slane, Baron McG, (Paris 1863-8, Imprimerie Impériale, 3 vols.), vol. i, p. 333).] Yathrib’s title to remain the seat of government for this vast realm was indisputable on its juridical merits. This remote oasis-state was the territorial nucleus out of which the Muslim Arab world-empire had burgeoned in its miraculously rapid growth, and it was now also hallowed as Madīnat-an-Nabī, the City of the Prophet which had recognized his mission and had furnished him with home, throne, and sepulchre. This title was so impressive that de jure Medina remained the capital of the Caliphate at any rate until the foundation of Baghdad by the ʿAbbasid Caliph Mansūr in A.D. 762. Yet de facto the swiftly expanding dominions of the Prophet Muhammad and his successors were governed from Medina for no longer than thirty-four years; for the fact was that this oasis hidden away in the interior of the Arabian Plateau – a vaster, wilder, barer, emptier counterpart of the Plateau of Iran – had condemned itself to political nullity by the immensity of its political success.
A Study of History, Vol VII, OUP, 1954