The city's fortifications were strong, with a wide moat and a thick wall protected by 44 towers, according to the contemporary geographer Ibn Khordadbeh, and the caliph assigned each of his generals to a stretch of the walls. Both besiegers and besieged had many siege engines, and for three days both sides exchanged missile fire while Arab sappers tried to undermine the walls. According to Arab accounts, an Arab prisoner who had converted to Christianity defected back to the caliph, and informed him about a place in the wall which had been badly damaged by heavy rainfall and only hastily and superficially repaired due to the city commander's negligence.
The city's defenses were robust, featuring a broad moat and a sturdy wall fortified by 44 towers, as noted by the contemporary geographer Ibn Khordadbeh. The caliph assigned each of his generals to different sections of the walls. Both attackers and defenders utilized numerous siege machines, and for three days both sides engaged in missile exchanges while Arab engineers attempted to undermine the walls. According to Arab accounts, an Arab convert who had previously converted to Christianity betrayed the city commander by revealing a section of the wall that was severely damaged due to heavy rainfall and only superficially repaired.