The tribal feuds which occupied the Arabs of Khurāsān left the princes of Transoxania free to regain their independence. It would seem even that Lower _T_ukhāristān was not only in part lost to the Arabs but that local forces took the offensive and raided Khurāsān. On the gradual restoration of order under Umayya, however, Lower _T_ukhāristān again recognised, at least in name, the Arab suzerainty[34]. Meanwhile, a strange episode had occurred in Chaghāniān. Mūsā, the son of ʿAbdullah ibn Khāzim, sent by his father to secure a safe place of retreat, had captured the strong fortress of Tirmidh, from which he continually raided the neighbouring districts. His exploits were worked up in popular story into an epic of adventure, in which legend has almost overlaid historical fact. The most fantastic exaggerations were devised in order to provide a suitable background for the incredible deeds of valour indulged in by the hero. But in truth his actual exploits were sufficiently amazing, and all the efforts of the forces of the local rulers (magnified in the legend to huge armies of “Turks and Hay_t_al and Tibetans”), although aided on one occasion by a force of Khuzāʿites, were unable to dislodge him. For fifteen years he remained in secure possession of his stronghold, a refuge for the disaffected from all sides, and a standing example of the helplessness of the rulers across the river.
In 77/696 Umayya re-opened the campaigns into Transoxania. An expedition to Khwārizm was successful[35], another across the Oxus narrowly escaped destruction. Balādhurī mentions, with doubtful accuracy, a successful raid on Khuttal, which may, however, only be a variant on this. An expedition directed against Bukhārā, which is said to have had Tirmidh as a second objective, was hurriedly abandoned on the fresh outbreak of revolt under Bukayr b. Wishā_h_ in Khurāsān. Though the revolt failed in its immediate object, a most serious situation had been created. Bukayr had endeavoured to rally the Persians to his side by promising all converts remission of Kharāj. The opportunity was undoubtedly seized by large numbers, and the pacification occasioned some negotiations between Umayya and Thābit b. Qu_t_ba, an influential noble who acted as spokesman for the mawālī of Eastern Khurāsān. Umayya’s reimposition of Kharāj, however, caused widespread unrest[36] and made prompt action necessary. ʿAbdul-Malik at once recalled his hapless kinsman (in 78) and made Khurāsān a dependency of ʿIrāq under the government of _H_ajjāj. This far-sighted governor had already dealt with a desperate situation of the same sort in ʿIrāq and reduced it to outward tranquillity. The same extreme measures that had been adopted there were not necessary in Khurāsān; its troubles were due less to insurgent mawālī than to the factions of Qays. _H_ajjāj was himself a strong Qaysite, but he was not the man to put party before the interests of the State. The first necessity was to appoint a governor who could be trusted to repress both forms of anarchy and in Muhallab such a man was available. His tribe of Azd was not yet strong enough in Khurāsān to cause the risk of opening a new channel for factional strife, and his military reputation fitted him for carrying out _H_ajjāj’s policy of active campaigning as an antidote to internal dissension. It is possible that _H_ajjāj had in mind from the first a definite conquest of Transoxania, but for a few years nothing more than sporadic raids took place.