Persians kept on raiding Iraq, which resulted in political instability in Iraq, as a result Muslims invaded Ahvaz in 638 which forced powerful Persian commander in chief, Hormuzan, to enter into peace negotiations with Muslims. Hormuzan agreed to accept Muslim suzerainty over Ahvaz province and agreed to rule as Muslim's vassal. Hormuzan broke peace agreement three time and each time was pardoned by Caliph Umar and the peace renewed, until the third time when on Umar's instructions his capital was besieged and he was taken prisoner and sent to Madinah to umar, where he apparently accepted Islam.