R ash id ▁( r . ▁ 7 8 6 – 8 0 9 ) ▁in ▁particular ▁was ▁the ▁most ▁ener get ic ▁of ▁the ▁early ▁Abb as id ▁r ul ers ▁in ▁his ▁purs uit ▁of ▁war fare ▁against ▁By z ant ium : ▁he ▁established ▁his ▁seat ▁at ▁Ra qq a ▁close ▁to ▁the ▁front ier , ▁he ▁complement ed ▁the ▁th ugh ur ▁in ▁ 7 8 6 ▁by ▁forming ▁a ▁second ▁def ensive ▁line ▁along ▁northern ▁Sy ria , ▁the ▁al - ' A was im , ▁and ▁was ▁re put ed ▁to ▁be ▁sp ending ▁altern ating ▁years ▁leading ▁the ▁H aj j ▁and ▁leading ▁a ▁campaign ▁into ▁An atol ia , ▁including ▁the ▁largest ▁expedition ▁assemble d ▁under ▁the ▁Abb as ids , ▁in ▁ 8 0 6 . ▁ ▁Cont inu ing ▁a ▁tr end ▁started ▁by ▁his ▁immediate ▁prede cess ors , ▁his ▁reign ▁also ▁saw ▁the ▁development ▁of ▁far ▁more ▁regular ▁contacts ▁between ▁the ▁Abb as id ▁court ▁and ▁By z ant ium , ▁with ▁the ▁exchange ▁of ▁emb ass ies ▁and ▁letters ▁being ▁far ▁more ▁common ▁than ▁under ▁the ▁Um ay y ad ▁r ul ers . ▁Despite ▁Har un ' s ▁host ility , ▁" the ▁existence ▁of ▁emb ass ies ▁is ▁a ▁sign ▁that ▁the ▁Abb as ids ▁accepted ▁that ▁the ▁By z antine ▁emp ire ▁was ▁a ▁power ▁with ▁which ▁they ▁had ▁to ▁deal ▁on ▁equal ▁terms " ▁( K enn edy ). ▁ ▁Civil ▁war ▁occurred ▁in ▁the ▁By