and under all these circumstances the Arabs had no longer cause to fear the numerical superiority of their opponents. They appear to have outflanked the Byzantines from the eastern side, cut their line of communication with Damascus, and by occupying the bridge over the Wādi-r-Ruḳḳād frustrated also their chances of retreat to the westward. Finally they forced them into the angle between the Yarmūk and the Wādi-r-Ruḳḳād. Those who were not killed here plunged down into the steep and deeply cut beds of the rivers, and those of the latter who had finally managed to escape across the rivers to Jakutha were annihilated by the Arabs on the other side, as, by occupying the bridge, they were enabled with ease to cross the Wādi-r-Ruḳḳād. The decisive stroke in these fights, extending over months, happened on 20 Aug. 636. With this terrible defeat of the Byzantines on the Yarmūk the fate of Syria was permanently decided. The last troops of Heraclius, collected with much trouble, had been thus completely destroyed, and the immediate advance of the Arabs on Damascus rendered impossible every attempt to collect others. Thus Damascus was occupied a second time by the Arabs in the autumn of the same year, and this time finally.
The government of Medina had, as we have already seen, attempted for about the space of a year to introduce a systematic occupation of the country in place of the former planless raids. This policy made it necessary that the army of occupation should have a supreme commandant, who should at the same time act as vicegerent of the Caliph. At the outset Khālid, who on account of his qualities had acquired the senior rank, was confirmed in this position, but in the brilliant general there was entirely wanting the diplomatic art of a pacificator attaining his ends by statesmanlike compromises. For this position one of the foremost men of the theocracy was required, an absolute confidant of the Caliph. Omar selected Abū 'Ubaida, one of the oldest and most esteemed of his companions, of whom we know that, for instance at the death of the prophet, he had played an important part. His task in face of the autocratic army-leaders was a difficult one; he arrived in Syria just before the battle of the Yarmūk, but was prudent enough to leave at this critical stage the supreme command for this battle to Khālid, who was so minutely acquainted with the conditions. Thereupon however he himself intervened, distributed the various military commandants throughout the entire land, and then personally advanced, in company with Khālid, towards the North. Baalbek, Emesa, Aleppo, Antioch, and the Arabian tribes residing in the north of Syria put no difficulties in the way of the conquest. The town of Ḳinnasrīn (Kalchis) alone was less easily dealt with. From northern Syria 'Iyāḍ ibn Ghanm was then subsequently detached to the East, and he subjected Mesopotamia (639-646) without meeting with much opposition. To the North, however, the Amanus formed for centuries the more or less constant boundary of the Caliph's dominions.
