▁of ▁A zer ba ij an , ▁Armen ia ▁and ▁C au cas ian ▁Alban ia . ▁The ▁battle ▁was ▁fier ce , ▁but ▁the ▁S as an ian ▁troops ▁lost ▁during ▁the ▁battle . ▁This ▁opened ▁the ▁gateway ▁for ▁the ▁Muslim s ▁to ▁enter ▁A zer ba ij an . ▁The ▁Muslim s ▁then ▁inv aded ▁A zer ba ij an ▁and ▁captured ▁Is f and i yar , ▁the ▁son ▁of ▁Far ru kh z ad . ▁Is f and i yar ▁then ▁promised , ▁in ▁return ▁for ▁his ▁life , ▁that ▁he ▁would ▁agree ▁to ▁surrender ▁his ▁est ates ▁in ▁A zer ba ij an ▁and ▁aid ▁the ▁Muslim s ▁in ▁defe ating ▁his ▁brother , ▁Bah ram . ▁Bah ram ▁was ▁then ▁defeated , ▁and ▁su ed ▁for ▁peace . ▁A ▁p act ▁was ▁drawn ▁up ▁according ▁to ▁which ▁A zer ba ij an ▁was ▁surrender ed ▁to ▁C ali ph ▁U mar ▁on ▁usual ▁terms ▁of ▁pay ing ▁the ▁annual ▁J iz ya . ▁ ▁Muslim s ▁settled ▁in ▁A zer ba ij an ▁as ▁they ▁did ▁in ▁many ▁parts ▁of ▁Iran . ▁According ▁to ▁the ▁Iran ian ▁A zer ba ij ani ▁historian ▁A hm ad ▁Kas ra vi , ▁more ▁Muslim s ▁settled ▁in ▁A zer ba ij an ▁compared ▁to ▁other ▁provinces ▁due ▁to ▁the ▁province ' s ▁pl ent iful ▁and ▁fert ile ▁past ures . ▁Local ▁revol ts ▁against ▁the ▁C ali ph ate ▁were ▁common ▁and ▁the ▁most ▁famous ▁of ▁these ▁revol