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 fortifications of the city were formidable, encompassing a deep moat and a substantial wall with 44 towers. Ibn Khordadbeh described them as such in his contemporary writings. Each general under the caliph's command was assigned a portion of the walls to defend. Both besiegers and defenders employed various siege devices, and for three days they exchanged missiles while Arab engineers worked on undermining the defenses. According to Arab sources, an individual who had previously converted to Christianity from Islam informed the caliph about a damaged section of the wall that had been hastily repaired due to negligence.