It was now the beginning of the twelfth year of the Hegira. Rebellion had been put down in the centre of Arabia, and the southern tribes were also in fair way to pacification. It was Abu Bekr’s policy to turn the victorious arms of the restless Arabs to similar work elsewhere. He therefore despatched two armies to the northern frontier. One of these, under command of Khâlid, joined by Mothanna, was to march on Obolla near the mouth of the Euphrates, and thence, driving the enemy up its western shore, to work its way towards Hîra, the capital of Irâc. Iyâdh, at the head of the other, was directed to Dûmat al Jendal, which had cast off its allegiance; and thence to pass also on to Hîra. Whichever of the two first reached and captured that city was to be in command of the country.[99] [Sidenote: Khâlid joins Mothanna in Irâc.] The progress of Iyâdh was hampered by his enemy, and he was long detained in the Jôf, or country about Dûma. Khâlid met with no such obstacle. His army, like Mothanna’s, was swelled on its march from Yemâma to Irâc by large bodies of Bedouins. These were of the greater service as his numbers had been thinned not only by the carnage at Yemâma, but also by the free permission, which, after their long and arduous campaign, the Caliph had given the army, of furlough to their homes. Nevertheless, the expedition was so popular that when Khâlid, after a flying visit to the Caliph at Medîna, rejoined his camp as it neared the mouth of the Euphrates, he found himself at the head of 10,000 men; and this besides the 8,000 of Mothanna, who hastened loyally to place himself under the great leader’s command. [Sidenote: The Syrian desert and Mesopotamia.]