Thus we find him in A.H. 98 conducting his troops against Jurjān and Tabaristān. The former country was regarded as the key of Western Asia. It was strongly fortified; and its walls, extending as far as the Sea of Azof, were an effectual barrier to the aggressions of the Turkish hordes.[143] But these attacks appear to have told severely on the inhabitants, who finally secured the withdrawal of their persistent foes by the payment of tribute. They had adopted similar tactics on an Arab invasion which took place under the Caliphate of `Othman: when the enemy again withdrew, on receiving a bribe of 2,000,000 direms. Jurjān thereafter enjoyed a long immunity from attack, although Kutayba had more than once solicited permission from Hajjāj to establish a direct route between `Irāk and Khorāsān by crushing its independence. Yezīd’s anxiety to achieve a conquest which had been the unrealised ambition of his great rival can be easily understood. On his departure from Jurjān he left his son Mokhallad in charge of Khorāsān. The force at his command included Kūfans, Basrans, Syrians, and the _élite_ of Khorāsān and Ray, and numbered 100,000, exclusive of volunteers and slaves. The first object of his attack was the town of Dihistān, which was peopled by Turks.[144] Having reduced it by a close blockade, he proceeded to Jurjān, where the inhabitants, as was their wont, bought peace at the price of 300,000 direms. Yezīd then passed in a south-westerly direction into Tabaristān. Its king took refuge in a mountain inaccessible to the Mohammedan troops, and organised resistance to the invader from this safe retreat. He obtained reinforcements from Gīlān and Daylam, and called on the _Marzabān_ of Jurjān to break the treaty entered into with Yezīd, and massacre the Arabs in Jurjān. Thus was Yezīd surrounded by active foes, and his retreat cut off. The only course open to him was to conclude peace with the king of Tabaristān, and gather his forces for the punishment of the faithless people of Jurjān. This he did, swearing that he would not stay his sword until he had shed blood enough to turn a mill, and had eaten bread made with flour therefrom. The Marzabān, on learning the approach of the Musulmans, shut himself up in a stronghold which crowned a mountain top, and was accessible by one road only. Here he held out for seven months against Yezīd; but the latter enticed the garrison from their retreat by a ruse, and made prisoners of them all. Their punishment enabled the ruthless conqueror to fulfil his pledge.