The practice of raising native levies, once started, appears to have become general in Khurāsān. We have no information as to when the local forces of Khurāsān and Lower _T_ukhāristān were incorporated in the army, nor in what proportions, but we have frequent evidence of their presence and increasing prestige in the wars of the next forty years[52]. On the other hand, though contingents from the towns of Sogdiana were used by later governors if they were available, as in 106 and 112 A.H., in view of the weaker hold of the Arabs on Transoxania Sogdian troops never formed a regular division of the Arab forces up to the end of the Umayyad period. This distinction between the two subject Iranian groups became, as will be seen, of some importance when the ʿAbbāsid propaganda began to tamper with the loyalty of the armies of Khurāsān. While Qutayba was occupied with the new organization of Bukhārā, a detached force, sent under ʿAbdur-Ra_h_mān from Kish to Samarqand to exact from _T_arkhūn the tribute agreed upon in the previous year, successfully accomplished its mission. ʿAbdur-Ra_h_mān, after restoring the hostages to _T_arkhūn, rejoined his brother at Bukhārā, whence they returned to Merv for the winter. One important vassal of _T_ukhāristān, who had long been a thorn in the side of _H_ajjāj, still remained unsubdued. This was Rutbīl or Zunbīl, the Turkish ruler of Zābulistān[53]. In 91, the viceroy united Sijistān to the province of Khurāsān, with instructions to Qutayba to undertake a campaign in person against Rutbīl. In the following year, therefore, the expeditions into Transoxania were interrupted, and the army again marched southwards. To Qutayba’s great relief (for he disliked to undertake a campaign against this formidable foe who had made Sijistān “an ill-omened frontier”) Rutbīl hastened to tender his submission, and at the same time sent an embassy to convey his homage to the Emperor of China[54]. Recognition of Arab suzerainty over Zābulistān involved of course only the payment of a fixed tribute, and no attempt was made at a permanent occupation.