7 4 7 ▁CE , ▁a ▁huge ▁revol t ▁against ▁the ▁Um ay y ad ▁C ali ph ate ▁occurred . ▁The ▁Um ay y ad ' s ▁were ▁eventually ▁defeated ▁by ▁the ▁Abb as id ▁army ▁under ▁the ▁rule ▁of ▁Ab u ▁Abb as ▁Abd ul lah ▁al - S aff ah ▁( see ▁Battle ▁of ▁the ▁Z ab ) ▁in ▁year ▁ 7 5 0 . ▁The ▁last ▁Um ay y ad ▁C ali ph , ▁Mar wan ▁II , ▁was ▁killed ▁in ▁a ▁less er ▁battle ▁a ▁few ▁months ▁after ▁the ▁Battle ▁of ▁the ▁Z ab , ▁thus ▁ending ▁the ▁Um ay y ad ▁C ali ph ate . ▁Historical ▁accounts ▁diff ers ▁on ▁what ▁happened ▁to ▁F ad ak ▁under ▁the ▁early ▁Abb as id ▁cal i ph s . ▁There ▁is ▁however ▁cons ensus ▁among ▁Islam ic ▁sch ol ars ▁that ▁F ad ak ▁was ▁granted ▁to ▁the ▁descend ants ▁of ▁F at im ah ▁during ▁Al - Ma ' mun ' s ▁reign ▁as ▁C ali ph ▁( 8 3 1 - 8 3 3 ▁CE ). ▁Al - Ma ’ mun ▁even ▁decre ed ▁this ▁to ▁be ▁recorded ▁in ▁his ▁( d ī w ā ns ). ▁▁ ▁Al - Ma ’ mun ' s ▁successor , ▁ ▁Al - M ut aw ak kil ▁( 8 4 7 - 8 6 1 ) ▁re capt ured ▁F ad ak ▁from ▁the ▁pro gen y ▁of ▁F at im ah , ▁dec ree ing ▁it ▁to