diversion by sending other columns against Rickka, Roha, Nisibîn, and such like strongholds in Upper Mesopotamia. Meanwhile the Romans landed from their ships. Antioch threw open her gates to them; and Kinnisrîn, Aleppo, and all the chief towns in the north, were in full revolt. Abu Obeida called a council of war; Khâlid was for giving battle, but he was alone in that view. Abu Obeida, feeling too weak to cope with the now combined forces of the Bedouins and Romans, retired within the walls of Hims, and, hemmed in by enemies, awaited the succour now advancing from Kûfa. So grave did Omar himself regard the crisis that, quitting Medîna for the second time, he journeyed to Jâbia, intending to march in person with the reinforcements northwards. But while on the journey, a change had already come over the scene. The vigorous movements in Mesopotamia so alarmed the Bedouins for the safety of their homes in the desert, that they began to forsake the Roman cause. [Sidenote: Abu Obeida puts the Romans and Bedouins to flight.]Seeing now his opportunity, Abu Obeida issued from the fortress, and after a severe engagement routed the enemy, who fled in such confusion that, even before the arrival of Cacâa, they were totally dispersed. Omar returned from Jâbia to Medîna. He was delighted at the result; and he specially commended the alacrity of the Kûfa column:--‘The Lord reward them,’ he wrote to Sád, ‘for their ready gathering and their speedy march to the succour of their beleaguered brethren.’[336] [Sidenote: Campaign in Mesopotamia and Asia Minor. A.H. XVII. A.D. 638.] It was the last effort of Constantinople to expel the invader from Syria, and the yoke plainly now was not to be shaken off. The expeditions undertaken for diverting the nomad insurgents had also the effect of reducing Mesopotamia to its uttermost limits. But not content with this, the infant faith, becoming conscious of its giant strength, began to stretch itself towards the north. The successes in Mesopotamia were followed up by a campaign in Asia Minor, under distinguished leaders; and the name of Iyâdh, the general-in-chief, under whom even Khâlid did not disdain to serve, begins to figure in the brief Byzantine record.[337] Nisibîn,[338] Amida, Harrân, Roha, and all the strong places lying along the northern frontier were taken or recaptured, and even Armenia was overrun.[339] [Sidenote: Christian tribes in Mesopotamia. The Beni Iyâdh.]