Islamic armies defeated the Sasanians in AD 642 at Nahavand (near modern Hamadan, Iran) and moved on to the Afghan area, but they were unable to hold the territory; cities submitted, only to rise in revolt, and the hastily converted returned to their old beliefs once the armies had passed. The 9th and 10th centuries witnessed the rise of numerous local Islamic dynasties. One of the earliest was the Tahirids of Khorasan, whose kingdom included Balkh and Herat; they established virtual independence from the 'Abbasid caliphate in AD 820. The Tahirids were succeeded in 867-869 by a native dynasty from Seistan, the Saffarids. Local princes in the north soon became feudatories of the powerful Samanids, who ruled from Bukhara. From 872 to 999 Bukhara, Samarkand, and Balkh enjoyed a golden age under Samanid rule.