taxes from the subjugated people that invited the numerous local rebellions. Medieval Islamic scholars divided modern-day Afghanistan into two regions - the provinces of Khorasan and Sistan. Khorasan was the eastern satrapy of the Sasanian Empire, containing Balkh and Herat. Sistan included a number of Afghan cities and regions including Ghazni, Zarang, Bost, Qandahar (also called al-Rukhkhaj or Zamindawar), Kabul, Kabulistan and Zabulistan. Before Muslim rule, the regions of Balkh (Bactria or Tokharistan), Herat and Sistan were under Sasanian rule. Further south in Balkh region, in Bamiyan, indication of Sasanian authority diminishes, with a local dynasty apparently ruling from the late antiquity, probably Hepthalites subject to the Yabgu of Western Turks. While Herat was controlled by Sasanians, its hinterlands were controlled by northern Hepthalites who continued to rule the Ghurid mountains and river valleys. The Arab Umayyads regularly claimed nominal overlordship over the Zunbils and Kabul Shahis, and in 711 Qutayba ibn Muslim managed to force them to pay tribute. They would also be conquered by the Saffarids and Ghaznavids. In Afghanistan, the frontier of the Islamic conquest had become more or less stationary by the end of the first century of Hijri calendar. One reason was that the relative importance of Sistan and Baluchistan had begun to diminish by the time of Mu'awiyah I, when the conquests of Bactria and Transoxania were undertaken. In addition, the conquest in the eastern direction was extended to Makran and Sind, with Muslim colonies becoming established there in 711–12. Sistan The earlier Arabs called Sistan as Sijistan, from the Persian word Sagestan. It is a lowland region, lying round and eastwards from the Zarah lake, which includes deltas of Helmand and other rivers which drain into it. The Muslim conquest of Sistan began in 23 AH (643-644 AD) when Asim bin Amr and Abdallah ibn Amir invaded the region and besieged Zaranj. The Sistanis concluded a treaty with Muslims, mandating them to pay the kharaj. The cash-strapped Sasanian king Yazdegerd III who had a large retinue, had fled to Kerman in 650. He had to flee from Kerman to Sistan after his arrogance angered the marzban of the place, eluding an Arab force from Basra which defeated and killed the marzban. Yazdegerd lost the support of governor of Sistan after demanding taxes from him and had to leave for Merv. It is not known whether this governor was a Sasanian prince or a