The garrison eventually surrendered and defected after the Byzantines received information about the fort being without supplies.
[1] A Roman assault against the fort was defeated with heavy losses, and the attackers were only saved by a well-directed charge by Ostrogothic cavalrymen.
As a result, Belisarius decided to institute a blockade by investing the fort, and in order to secure his besieging forces, he dispatched the Ghassanid Arabs under Al-Harith ibn Jabalah to raid the region across the Tigris river.
[a] Apparently, he did not trust the Arab king, and sent 1,200 Roman regulars, mostly his own hypaspistai, to accompany the raiding part.
[2] The sweltering heat of Mesopotamia caused serious illness in the Roman camp, which forced Belisarius to halt the campaign.