Arab legend relates that the Muslim forces, pursuing Yazdigird from the field of Nihāwand in 21/642, had already come in contact with the “Turks” of _T_ukhāristān before the death of ʿOmar. But the final destruction of the Sāsānid power and first imposition of Arab rule on Khurāsān only followed ten years later, by the troops of ʿAbdullah ibn ʿĀmir, ʿOthmān’s governor in Ba_s_ra. The Ephthalites of Herāt and Bādghīs submitted without a blow, and the first serious check to their advance was met in the Murghāb valley, when al-A_h_naf b. Qays with an army of 4,000 Arabs and 1,000 Persians found himself opposed by the organised forces of Lower _T_ukhāristān and was compelled to retire on Merv-Rūdh. A second expedition under al-Aqraʿ b. _H_ābis, however, defeated a weaker force in Jūzjān, and subsequently occupied Jūzjān, Fāryāb, _T_ālaqān, and Balkh. Small divisions made plundering raids into the neighbouring territories, _e.g._, to Siminjān (a town within the frontiers of _T_ukhāristān proper, governed by a Turkish prince, the Ruʿb Khān), and to Khwārizm, not always with success; on the other hand, a successful raid was made on Māyamurgh in Sogdiana in 33/654, which is mentioned by Abū ʿUbayda alone of the Arabic authorities[21]. A general insurrection which broke out shortly afterwards, headed by a certain Qārin, apparently a member of the noble Persian family bearing that name, seems to have been instrumental in causing the Arabs to evacuate Khurāsān for a time[22], though several raids are recorded of ʿAlī’s governors between 35 and 38 A.H. These earliest “conquests,” in fact, were little more than plundering raids on a large scale, the effect of that movement of expansion whose momentum was carrying forward the Arabs irresistibly. According to the Chinese records, which, however, require to be used with caution at this point, the retreat of the Arabs in 655 was followed up by the army of _T_ukhāristān who reinstated Pērōz, the son of Yazdigird, as titular king of Persia[23].