against Tabūk, which had to be subjected two years before the death of the prophet, that created friendly relations with at least a few of the tribes on the southern boundary of Palestine. In the war of conquest the great tribes of the former boundary State of the Ghassānids still fought on the side of the Byzantines. The tribes to the south of the Dead Sea however, such as the Judhām and Ḳuḍā'a, who commanded the route from Medina to Gaza, had every reason for connecting themselves more closely with Medina. Previously they had been in the pay of the Byzantines, and being moreover Christians, they had no intention of allying themselves with the Muslims. Soon after the battle of Mu'ta however, we are informed, the Emperor Heraclius, who at that time was in great financial difficulties owing to the debt contracted with the Church for the great Persian war, suspended the yearly subsidies to the Bedouins on the southern boundary, probably thinking that with the new political situation he might venture on this economy. At that time even a far-seeing politician could not have regarded as serious the organisation of the ever-divided Arabs living in the interior of Arabia. Judging by the behaviour of the northern tribes, they continued for a time to be paid. Theophanes even treats the suspension of subsidies as being in some way the cause of the summoning of the Muslims. Apart from this may be added that, after the victories of Khālid in Central Arabia, these border tribes, like the Bakr ibn Wā'il in the East, were led into a dilemma; as Byzantium withdrew the subsidies from them it was only natural that they made an alliance with the Muslims to recoup themselves by plundering raids.
Their suggestion met with the approval of the Caliph, who probably recognised that the commotion which had been raised must be diverted in some direction or other. The Medina people themselves, according to Arabian reports, do not appear to have at first displayed any enthusiasm for such a risky action; probably they had not forgotten the disaster of Mu'ta. Nevertheless in the autumn of 633 various small detachments were sent off into Syria, the first under Yazīd ibn Abī Sufyān, a brother of the subsequent Caliph Mu'āwiya, the second under Shuraḥbīl ibn Ḥasana, the third under 'Amr ibn al-'Āṣ. The first two bodies of troops, probably co-operating most of the time, took the direct track via Tabūk-Ma'ān; 'Amr marched along the coast via Aila ('Aḳaba); other smaller companies followed later and pushed forward from the South into the country east of the Jordan. The first to get engaged in battle was Yazīd. Approaching from westward he ascended the hills surmounting the Wādī 'Araba, the great valley south of the Dead Sea, and surprised several thousands of Byzantine troops under the Patricius of Caesarea, named Sergius. These were routed and compelled to retire on Gaza; before reaching this town however they were overtaken (4 Feb. 634) by the Arabs and annihilated, Sergius also losing his life. After this success Yazīd again retired beyond the protecting Dead Sea. Shortly
