The Conquest of Isfahan
With regard to the conquest of Isfahan, it is written that it was assigned to Abdullah bin Abdillah. He was in Nahawand when he received a letter from Hazrat Umar (ra) which stated that he should advance towards Isfahan and appoint Abdullah bin Waraqah Rihaee as head of the vanguard and to appoint Abdullah bin Waraqah Asadi and Asmah bin Abdillah to command the flanks. On the outskirts of Isfahan, they came up against a contingent under the command of the Persian commander Astandar. The commander of the enemy vanguard was Shahr Baraz Jazwiah, an experienced and elderly man. He attacked the Muslims with his contingent and a fierce battle ensued. Jazwiah called out for a duel as a result of which Abdullah bin Waraqah stepped up and killed him. After an intense battle, the enemy suffered defeat and fled. The commander-in-chief, Astandar entered into an agreement with Abdullah bin Abdillah.
Next, the Islamic army advanced towards Isfahan, which was known as Jae, and laid siege of the city. One day, the governor of the city, Fazusfan came outside and said to Abdullah bin Abdillah, commander of the Muslim army, “Instead of both armies fighting, let us fight a duel; whosoever overcomes their rival will be the winner.”
Abdullah accepted this proposal and enquired whether he would strike first or should he. Fazusfan attacked first but Abdullah stood resolute. Owing to the strike of the enemy, Abdullah’s saddle of his horse was cut. Abdullah sat firmly on the bare back of his horse and before he launched his attack, he said to Fazusfan, “Remain there.” Fazusfan said, “You are an extremely intelligent and brave man. I am ready to enter into an agreement and hand the city over to you.” Thus, they entered a treaty and the Muslims gained control of the city. According to Tabari, this conquest took place in 21 AH.
(Muhammad Ibn Jarir al-Tabari, Tarikh al-Tabari, Vol. 2 [Beirut, Lebanon: Dar al-Kutub al-Ilmiyyah, 2012], pp. 531-532)
The historian Baladhuri has stated that rather than Abdullah bin Abdillah being appointed as the commander of the Muslim army in this battle, it was Abdullah bin Budail bin Waraqah Khuza‘i.
(Futuh al-Buldan, p. 188, Dar al-Kutub al-Ilmiyyah, Beirut, 2000)
The historian, Tabari writes that some people have confused Abdullah bin Waraqah Asadi – who participated in the battle and was the commander of one of the flanks – with Abdullah bin Budail bin Waraqah, whereas in the time of Hazrat Umar (ra) he was very young, and during the Battle of Siffin, he was killed at the age of 24.
(Tarikh Islam ba Ahd Hazrat Umar (ra), Syed Mir Mahmood Ahmad Nasir Sahib, p. 136-138) 2009], pp. 166-168)
Then there was the rebellion and recapturing of Hamadan. After the battle of Nahawand, the Muslims also conquered Hamadan. The people of Hamadan then violated the peace treaty by assembling an army with military support from Azerbaijan. Hazrat Umar (ra) instructed Nuaim bin Muqarrin to go there with an army of 12,000. After a fierce battle, the Muslims conquered the city.
(Ali Muhammad al-Salabi, Sirat Amir al-Momineen Umar bin al-Khattab (ra) [Beirut, Lebanon: Dar al-Ma‘rifah, 2007] p. 431)
Hazrat Umar (ra) was especially worried about the result of this battle. The messenger brought glad tidings of the victory. Hazrat Umar (ra) then sent him back with the instructions to Nuaim bin Muqarrin to appoint someone as his deputy in Hamadan, and to then advance to Rayy. There he had to defeat the army and remain there, as it was central to all the areas around it.
(Tarikh Islam ba Ahd Hazrat Umar (ra), Syed Mir Mahmood Ahmad Nasir Sahib, p. 136-138 [2009], p. 169)