A siege of the Byzantine capital of Constantinople in 626 was unsuccessful, and Heraclius, now allied with Turks, started a risky but successful counterattack deep into Persia's heartland.

"[4] His name in combination with the epithet Abarwēz is attested in Georgian as K‛asre Ambarvez (Pseudo-Juansher, writing around the year 800)[5] and in Armenian as Aprouēz Xosrov.

Bahram, infuriated by Hormizd's actions, responded by rebelling, and due to his noble status and great military knowledge, was joined by his soldiers and many others.

[9] The legitimacy of the House of Sasan was based on acceptance that the halo of kingship, the xwarrah, was given to the first Sasanian shah, Ardashir I (r. 224–242) and his family following the latter's conquest of the Parthian Empire.

[14] Khosrow then took a carrot and stick attitude, and wrote a message to Bahram Chobin, stressing his rightful claim to the Sasanian kingship: "Khosrow, kings of kings, ruler over the ruling, lord of the peoples, prince of peace, salvation of men, among gods the good and eternally living man, among men the most esteemed god, the highly illustrious, the victor, the one who rises with the sun and who lends the night his eyesight, the one famed through his ancestors, the king who hates, the benefactor who engaged the Sasanians and saved the Iranians their kingship—to Bahram, the general of the Iranians, our friend.... We have also taken over the royal throne in a lawful manner and have upset no Iranian customs.... We have so firmly decided not to take off the diadem that we even expected to rule over other worlds, if this were possible....

[9] Bahram Chobin tried to support his cause with the Zoroastrian apocalyptic belief that by the end of Zoroaster's millennium, chaos and destructive wars with the Hephthalites/Huns and the Romans occurs and then a savior would appear.

He started minting coins, where he is on the front imitated as an exalted figure, bearded and wearing a crenellation-shaped crown with two crescents of the moon, whilst the reverse shows the traditional fire altar flanked by two attendants.

"[21] Bahram Chobin in his letter promised that the Armenians would become partners of the new Iranian empire ruled by a Parthian dynastic family if he accepted his proposal to betray Khosrow II.

[9][23] Bahram Chobin became a highly popular figure after saving the Khagan from a conspiracy instigated by the latter's brother Byghu (conceivably an incorrect translation of yabghu).

[1] The Arab Lakhmids/Nasrids, a client state located at al-Hira and its surroundings, could now openly convert to Nestorian Christianity without angering the Sasanian court.

[citation needed] After his victory, Khosrow rewarded his uncles with high positions: Vinduyih became treasurer and first minister and Vistahm received the post of spahbed of the East, encompassing Tabaristan and Khorasan, which was the traditional homeland of the Ispahbudhan.

The Sasanian monarchs' traditional mistrust of over-powerful magnates and Khosrow's personal resentment of Vinduyih's patronising manner certainly contributed to this decision.

Vistahm repelled several loyalist efforts to subdue him, and he soon held sway in the entire eastern and northern quadrants of the Iranian realm, a domain stretching from the Oxus river to the region of Ardabil in the west.

Nevertheless, Vistahm's troops managed to repel the royal army at Qumis, and it required another expedition by Smbat in the next year to finally end the rebellion.

606/607, Khosrow recalled Smbat IV Bagratuni from Sasanian Armenia and sent him to repel the Turko-Hephthalites, who had raided as far as Spahan in central Iran.

[41]In 622, despite the major progress the Sasanians were making in the area of the Aegean Sea, the Byzantine Emperor Heraclius was able to take the field with a powerful force.

On top of that, the Iranians, who were siege warfare experts, were unable to transport their troops and equipment to the other side of the Bosphorus where their Slavic and Avar allies were located, due to heavy guarding of the strait by the Byzantine navy.

[45] Sheroe, with Aspad Gushnasp leading his army, captured Ctesiphon and imprisoned Khosrow II in the house of a certain Mehr-Sepand (also known as Maraspand).

Sheroe, who had now assumed the dynastic name of Kavad II, then ordered Aspad Gushnasp to lead the charge of accusations against the deposed shah.

The murder of all his brothers, "all well-educated, valiant, and chivalrous men",[7] stripped the Sasanian dynasty of a future competent ruler, and has been described as a "mad rampage" and "reckless".

[47] The overthrow and death of Khosrow culminated in a chaotic civil war, with the most powerful members of the nobility gaining full autonomy and starting to create their own government.

[54] Since the 5th century, the Sasanian monarchs had been made aware of the significance of the religious minorities in the realm, and as a result tried to integrate them into a structure of administration where, according to legal principles, all would be treated straightforwardly as mard / zan ī šahr, i.e. "man/woman [citizen] of the country".

According to Nina Garsoïan, Khosrow "returned to the normal pattern of alternate toleration and repression" of Christians after the death of his ally Maurice in 602.

[60] Mushegh II Mamikonian, a prominent Armenian nakharar, is the first and only Christian nobleman that is praised by courtly historiographers, due to his rejection of the enticements of Bahram Chobin.

[60] Smbat IV Bagratuni likewise led an illustrious career under Khosrow, rising to the office of frontier commander of Gurgan, possibly the most vital and contested area of the Sasanian realm.

[62] The lower section depicts Khosrow II on horseback, wearing full body armor, whilst holding a lance and shield.

[1][62] On the left side panel, a boar hunt scene is depicted, portraying Khosrow on a boat whilst aiming a bow.

[63] According to Shayegan, Khosrow's adoption of the title was "undoubtedly a consequence of his Byzantine policy," and was signifying a resurrection of the ancient Achaemenid Empire.

Muhammad reportedly changed the subject, made it obvious he did not like their appearance, and responded by asking why they shave their beards and leave their mustaches to grow and be that large.

[70] The battles between Heraclius and Khosrow are depicted in a famous early Renaissance fresco by Piero della Francesca, part of the History of the True Cross cycle in the church of San Francesco, Arezzo.