Oshrusana

Osrūshana (Persian: اسروشنه‎‎) or Oshrūsana (Persian اُشروسنه - Ošrūsana), also known as Istarawshan (at present) Sudujshana, Usrushana, Ustrushana, Eastern Chao, was a former Iranian region in Transoxiana. The Oshrusana lay to the south of the great, southernmost bend of the Syr Darya and extended roughly from Samarkand to Khujand. The capital city of Oshrusana was Banjikat. The exact form of the Iranian name Osrušana is not clear from the sources, but the forms given in Hudud al-'alam, indicate an original *Sorušna.

The rulers of the Oshrusana or Ustrushana (Istarawshan) went by the title of "Afshin", and the most famous of whom was Khedār (Arabicised Haydar) b. Kāvūs. Our early knowledge of the ruling family of Oshrusana is derived from the accounts by the Islamic historians (Tabari, Baladhuri, and Ya'qubi) of the final subjugation of that region by the 'Abbasid caliphs and the submission of its rulers to Islam.

During the time when the first Arab invasion of the country took place under Qutayba b. Muslim (94-5/712-14), Ushrusana was inhabited by an Iranian population, ruled by its own princes who bore the traditional title of Akhshid or Afshin. The first invasion by the Arabs did not result in them controlling the area.

According to the Encyclopedia of Islam:

In 119 AH/737 AD the Turkic enemies of the governor Asad b. Abdallāh al-Ghasrī fell back on Usrūshana (al-Tabarī, ii, 1613). Nasr b. Sayyār subdued the country incompletely in 121/739 (al-Balādhurī, 429; al-Tabarī, ii, 1694), and the Afshin again made a nominal submission to Mahdī (al-Yaqūbī, Tarīkh , ii, 479).

...
Wikipedia