very near to the attainment of their plan; twice under Mu'āwiya, the first occasion being principally a land expedition under Faḍāla, who conquered Chalcedon (668), and from thence in the spring of 669, in combination with the Caliph's son Yazīd, who had advanced to his help, besieged Constantinople. These land expeditions were in vain, and equally so were the regular, so-called seven years' fights between the fleets of the two powers, these lasting from 674 or even earlier until the death of Mu'āwiya (680), and taking place immediately before Constantinople, where the Arabs had secured for themselves a naval base. When at a later date, after the termination of the civil wars, the second great wave of expansion set in under the Caliph Walīd, Constantinople again appeared attainable to them. The remarkable siege of Constantinople, which lasted at least a year (716-717), took place, it is true, afterwards under Walīd's successor, the Caliph Sulaimān. This also ended unsuccessfully for the Arabs. The Arabian boundary remained as before mainly the Amanus and the Caucasus, and beyond that the limits of their dominion varied. But all these regular wars are connected in the closest degree with the internal history of the Byzantine empire, and for this reason they are treated in detail elsewhere. Saracens in this quarter came rather early to the frontier which for a considerable time they were destined not to cross.
The connexion of matters has compelled us whilst reviewing the relations between the Saracens and the Byzantines to anticipate other events in the dominions of the Caliphate. We now return to the reign of the Caliph Omar, under whom and his successor the expansion reached limits unchanged for a considerable time, for we cannot gain from the delineation of the mere outward expansion of the Saracens any satisfactory conception of the Arabian migration, which completely metamorphosed the political contour of the Mediterranean world. Even the interest of the student, in the first instance directed to the West, must not overlook the civil wars in the young Arabian world-empire, for they are in even greater degree than either Byzantines or Franks responsible for bringing to a standstill the movement which threatened Europe. By doing so we at the same time notice the beginnings of Muslim civilisation. If we fail truly to estimate this the continuity postulated at the commencement of our chapter becomes obscured, and the great influence of the East on western countries in the Middle Ages remains incomprehensible.
Omar died at the zenith of his life, unexpectedly struck down in the midst of his own community by the dagger of a Persian slave (3 Nov. 644). While Abū Bakr had decreed him as his successor simply by will, because the succession was felt on all sides to be evident, the dying Omar did not venture to entrust any particular one of his fellow-companions with the succession. This strict, conscientious, and sincerely religious man did not dare in the face of death to discriminate between the
