Sasanian civil war of 589-591

The Sasanian civil war of 589-591 was a conflict that broke out in 589, due to the great deal of dissatisfaction among the nobles towards the rule of Hormizd IV. The civil war lasted until 591, with ended with the overthrow of the Mihranid usurper Bahram Chobin and the restoration of the Sasanian family as the rulers of Iran.

Background
When Khosrau I ascended the Sasanian throne in 531, he began a series of reforms that was started by his and predecessor Kavadh I. These reforms were mostly aimed at the elites of the Sasanian Empire, who had become too powerful and had been able to depose several Sasanian rulers. Khosrau was quite successful in these reforms, and after his death in 579, he was succeeded by his son Hormizd IV, who continued his father's policies, but in a harsher way; in order to control the elites, he, in the words of Shapur Shahbazi, "resorted to harshness, denigration, and execution." Hormizd IV was extremely hostile to the elites and did not trust him, therefor, he constantly sided with the lower classes.

Hormizd IV also declined the requests of the Zoroastrian priesthood to persecute the Christians, and like the elites, Hormizd IV did not like the Zoroastrian priesthood either, and therefor killed a great deal of them, including the chief priest (mowbed) himself. Furthermore, Hormizd IV also greatly reduced the payment of the military by 10 percent, and massacred many powerful and prominent members of elite, which included the famous Karenid vizier of his father, Bozorgmehr, including the latter's brother Simah-i Burzin; the Mihranid Izadgushasp; the army chief (spahbed) Bahram-i Mah Adhar, and the Ispahbudhan Shapur, who was the father of Vistahm and Vinduyih. According to the medieval Persian historian Al-Tabari, Hormizd is said to have ordered the death of 13,600 nobles and religious members.

The rebellion of Bahram Chobin
In 588, a massive Hephthalite-Turkic army invaded the Sasanian province of Khorasan. Bahram Chobin, a military genius from the House of Mihran, one of the seven Parthian clans, was appointed as the spahbed of Khorasan and the head of an army which included 12,000 soldiers. He then made a counter-attack against the Turks, and successfully defeated them, killing their ruler Bagha Qaghan. After some time, however, Bahram was defeated by the Byzantine Empire in a battle on the banks of the Aras River. Hormizd IV, who was jealous of Bahram Chobin, used this defeat as an excuse to dismiss Bahram Chobin from his office, and had him humiliated.

The coup in Ctesiphon and the march of Bahram Chobin
Bahram Chobin, furious of Hormizd actions, responded by rebelling, and due to his noble status and great military knowledge, was joined by his soldiers and many others. He then appointed a new governor for Khorasan, and afterwards set for Ctesiphon, the capital of the Sasanian Empire. Meanwhile, Hormizd tried to come to terms with Vistahm and Vinduyih, who hated Hormizd just as much as Bahram Chobin did. Hormizd shortly had Vinduyih imprisoned, while Vistahm managed to flee from the court. After a short period of time, a palace coup under the two brothers occur in Ctesiphon, which resulted in the blinding of Hormizd and the accession of the latter's son Khosrau II. The two brothers shortly had Hormizd killed.

Khosrau's flight to Byzantium and restoration
In order to get the attention of the Byzantine emperor Maurice (r. 582–602), Khosrau II went to Syria, and sent a message to the Sasanian occupied city of Martyropolis to stop their resistance against the Byzantines, but with no avail. He then sent a message to Maurice, and requested his help to regain the Sasanian throne, which the Byzantine emperor agreed with; in return, the Byzantines would re-gain sovereignty over the cities of Amida, Carrhae, Dara and Miyafariqin. Furthermore, Persia was required to stop intervening in the affairs of Iberia and Armenia, effectively ceding control of Lazistan to the Byzantines.

In 591, Khosrau moved to Constantia, and prepared to invade the Sasanian controlled part of Mesopotamia, while Vistahm and Vinduyih were raising an army in Azerbaijan under the observation of the Byzantine commander John Mystacon, who was also raising an army in Armenia. After some time, Khosrau along with the Byzantine commander of the south, Comentiolus, invaded Mesopotamia. During this invasion, Nisibis and Martyropolis quickly defected to them, and Bahram's commander Zatsparham was defeated and killed. During the same period, Khosrau, feeling disrespected by Comentiolus, convinced Maurice to replace the latter with Narses as the commander of the south. Khosrau and Narses then penetrated deeper into Bahram's territory, seizing Dara and then Mardin on February, where Khosrau was re-proclaimed king. Shortly after this, Khosrau sent one of his Iranian supporters, Mahbodh, to capture Ctesiphon, which he managed to accomplish.

Meanwhile, Khosrau's two uncles and John Mystacon, conquered northern Azerbaijan, and went further south in the region, where they defeated Bahram at Blarathon, who fled the Turks of Ferghana. However, Khosrau managed to deal with him by either having him assassinated or convince the Turks to execute him.

Peace with the Byzantines was then officially made. Maurice, for his aid, received much of Persian Armenia and western Georgia, and received the abolition of tribute which had formerly been paid to the Sasanians.