 From Ancyra , the Abbasid army turned to Amorium , to which they laid siege on 1 August . The siege was fiercely contested , even after the Abbasids , informed by a defector , effected a breach in a weak spot of the wall . After two weeks , however , taking advantage of a short truce requested by the Byzantine commanders of the breach for negotiations , the Abbasid army stormed the city . The city was thoroughly plundered and its walls razed , while the populace , numbering into the tens of thousands , was carried off to be sold into slavery . According to al @-@ Tabari , al @-@ Mu 'tasim now pondered extending his campaign to attack Constantinople , when the conspiracy headed by his nephew , al @-@ Abbas , was uncovered . Al @-@ Mu 'tasim was forced to cut short his campaign and return quickly to his realm , without bothering with Theophilos and his forces , encamped in nearby Dorylaion . Taking the direct route from Amorium to the Cilician Gates , both the caliph 's army and its prisoners suffered in the march through the arid countryside of central Anatolia . Some captives were so exhausted that they could not move and were executed , whereupon others found the opportunity to escape . In retaliation , al @-@ Mu 'tasim , after separating the most prominent among them , executed the rest , some 6 @,@ 000 in number . 
