Kavad II

Map of the metropolis of Ctesiphon

It was essential for the conspirators to move quickly to catch Khosrow II and his men off guard.[12] To maintain contact between Ctesiphon and Veh-Ardashir, it was necessary to occupy the pontoon bridge over the Tigris River. The core of individuals involved in the conspiracy had to grow as quickly as feasible. To gather more support, they had to make the political equivalent of a shock attack. The conspirators agreed to stage the coup on the night of 23/24 February.[13] They made the decision to inform Heraclius of the situation by sending a group of deputies to him. They required assurance that the Byzantines would be prepared to talk peace terms with a newly established Iranian government. They must have felt encouraged by Heraclius' recent proposition to Khosrow II, but they required a clear promise from him. Much justification for the coup attempt would be gone if there was no assurance that the Byzantines would also favor making peace, as the Sasanian state would get weakened by the coup.[13]

Four army commanders and two high-ranking civilians made up the deputation that departed. The hazarbed Gousdanaspa Razei was in charge of it. Once Heraclius had given the desired assurance, Gousdanaspa Razei was permitted to tell him about the details of the scheme, the upcoming coup, and its date. The deputation needed about a week's worth of time because the Byzantine army was about 200 kilometers from Ctesiphon. They thus must have departed by 17 February to be in time for the coup on 23/24 February.[13] They met with Heraclius in Shahrazur, most likely around 19 February. There they received his assurance, and in return informed him of the details of the coup.[14]

At night, a group of distinguished state officials brought Sheroe into Veh-Ardashir. Along with removing the horses from the royal stables and transporting them over the river, the conspirators from Ctesiphon crossed the bridge to meet him. A messenger called attention to Sheroe's takeover of authority and called for people to join his cause. The prisoners were freed, being told that the new shahanshah had opened the "gates of life" for them. They stole the horses from the royal stables and rode on them around while displaying their chains and berating Khosrow II. Instead of lending the coup military power, their main role was to intensify the revolutionary climate through their yelling and galloping. Heraclius had previously suggested that the conspirators free and arm the Byzantine prisoners of war, though there is no proof that they followed his advice.[14]

The palace guards were made aware of the situation by the ruckus coming from Veh-Ardashir, and several of them crossed the bridge to join the rebels. Khosrow II inquired about the commotion and trumpet noise. He tried to flee after learning the truth from his attendants but discovered that the royal stables were empty.[14] The last of the guards fled as the rebels crossed the river around daybreak and moved toward the palace. Khosrow II disguised himself and went to the palace's gardens, where he hid. A search crew discovered him there; he was then apprehended, cuffed, and imprisoned in the new treasury building.[15] The following day, on 25 February, Sheroe ascended the throne, adopting "Kavad" as his regal name.[6][16]

Folio from the Shahnameh depicting the enthronement of Kavad II. Created in 1518 in Tabriz, Safavid Iran

The conspirators that overthrew Khosrow II and installed Kavad II on the throne were composed of several powerful dynastic factions; the Nemrozi faction led by Mihr Hormozd; Shahrbaraz, who represented a branch of the Mihran family; the House of Ispahbudhan represented by Farrukh Hormizd and his two sons Rostam Farrokhzad and Farrukhzad; the Armenian faction represented by Varaztirots II Bagratuni; and the Kanarangiyan. At this juncture, the Iranian army had been split into three separate armies; the army of Adurbadagan led by Farrukh Hormizd; the occupation army of Shahrbaraz; and the army of Nemroz, led by Mihr Hormozd.[5]

Right after Kavad II's accession, the grandees pressured him to have Khosrow II executed, telling him that "It is not fitting that we should have two kings: either you kill Khosrow, and we will be your faithful and obedient servants, or we shall depose you and give our obedience to him [Khosrow] just as we always did before you secured the royal power."[17] Kavad II, terrified and devastated, dispatched Asfadjushnas as a deputy to Khosrow II.[18] Asfadjushnas' task was to explain to Khosrow II all the crimes he had committed, and the reasons for his removal and eventual execution. The lengthy discussion between the two is recounted by al-Tabari. Agitated, Kavad II ordered his father to be executed. Although various figures wanted vengeance upon Khosrow II, no one dared to commit regicide. Mihr Hormozd eventually volunteered.[19] He was the son of Mardanshah, the former padgospan of Nemroz, who had at his own request been executed by Khosrow II, due to being mutilated and dishonored by the latter.[20] Khosrow II was executed on 28 February 628.[16]

It was also either during this period or later, that Kavad II had all his brothers (17 or 18 of them) executed.[lower-alpha 4][6] This was done at the instigation of his minister Piruz Khosrow and Shamta, the son of Khosrow II's treasurer Yazdin.[22][23] Al-Tabari describes the executed brothers as "men of good education, bravery, and the manly virtues".[24] He adds that Kavad II was scolded by his sisters Boran and Azarmidokht for his actions, which caused him to become remorseful.[25]

Following his accession, Kavad II sent two groups of deputies to inform Heraclius of his victory. The first group was composed of a Persian and an Armenian, sent in advance to make preparations for the safe passage of the other group, led by Chosdaï, a high-rank royal secretary. The first group met with Heraclius on 24 March, where they gave him a letter from Chosdaï, which said that the latter was on his way with a group of delegates from the government and would be bringing written suggestions from the new shahanshah.[26] On 3 April, Heraclius met with Chosdaï, who gave him a letter from Kavad II as well as lavish gifts.[27] There Chosdaï provided thoroughly thought-out peace offers. After consolidating his position, Kavad II had turned to the Sasanian Empire's most influential constituency—the noble estate—for formal permission to begin peace negotiations with the Byzantines. This was easily gained, as the coup against Khosrow II owed its success to the extensive war-weariness and vehement dissatisfaction at many of the policies implemented in order to prolong the war effort.[28]

It was acknowledged that the majority of Khosrow II's enormous territorial gains would need to be given up. However, it was not what the exact frontier line should look like. Although Byzantium and Iran had been neighbours for a very long time, a precise definition of their geographic boundaries had not been established. Arguments could be made in favor of all of the several frontiers that had separated their lands since the resurgence of Iranian authority in the middle of the 3rd-century, due to the lack of any evident topographical, ethnic, or cultural line of boundary south or north of the Armenian Taurus Mountains.[28]

Map of the Byzantine-Iranian frontier during Late Antiquity before the war of 602–628

The letter sent by Kavad II to Heraclius from this period has partly survived in the Chronicon Paschale. In it, he labels Heraclius as "the most clement Roman emperor, our brother" in contrast to Khosrow II's belittling message towards the latter. By using the word "brother", Kavad II made it clear right away that he acknowledged the Byzantine Empire as legitimate and equals of Iran. He was thus swiftly re-establishing the dualistic world order that had been dominant for four centuries.[28] He announced his ascension to the throne of his fathers and forefathers via the protection of God in the letter's body, which was kept brief. Kavad II was doing everything in his power to avoid supporting the idea that the war had been a religious conflict by omitting mention of the divinities in Zoroastrianism.[29]

He claimed that he intended to free every individual held in jail, including political opponents of his father and prisoners of war, as a sign of his commitment to doing whatever could be helpful and in the service of mankind. The letter did not discuss how to fix the borders. Instead, Chosdaï had to relay the Sasanian offer to withdraw from Byzantine territory verbally, and Heraclius had to respond in writing with precise suggestions on how to fix the borders. A solemn oath, sealed in the customary Persian fashion with salt, was placed within the letter.[30]

Heraclius responded with a letter four days later, which has also partly survived. In the first portion, only the final few words of each line have been preserved. He confirmed receiving the letter brought by Chosdaï, congratulated Kavad II on becoming king (mentioning both God's role and Kavad II's good fate), and wished him many years of success, vigor, and peace. He also recognized Kavad II's stated intention to work in the service of mankind. The rest of Heraclius' letter has not survived.[30]

The English historian James Howard-Johnston suggests that the rest of Heraclius' letter was a general statement, in which he said that he was prepared to make peace, along with some indication of what he thought should be a fair boundary to draw between the two empires. In accordance with the conditions of his earlier offer, Kavad II would then be required to make arrangements for the Iranian soldiers' withdrawal from what was acknowledged to be Byzantine land and the release of all Byzantine prisoners of war. This is all implied in the History of Khosrov, a source that Howard-Johnston considers to be the "only trustworthy account of the second stage of negotiations." The Byzantine writer Nikephoros I claims that in the letter Heraclius called Kavad II his "son," thus declaring superiority over the Sasanian Empire. Howard-Johnston dismisses this claim, amongst other things arguing that due to the weakened Byzantine military, Heraclius was in no position to make such an assertion.[31]

After the negotiations were successful, Kavad II started carrying out the agreement's obligations. He gave orders for a letter to be written, telling Shahrbaraz to assemble his troops and head back to Iranian land, which he refused. According to Howard-Johnston, Shahrbaraz—having conquered the Byzantine Middle East—was not willing to give up more or less everything he had achieved in order to stop more violence and expenditure.[32] However, the Iranologist Parvaneh Pourshariati suggests that Shahrbaraz's noncompliance was due to his concern of the collaboration of the other factions of Iran, who were managing the affairs of the state while he was still in Byzantine territory.[33] Shahrbaraz's refusal led to a deadlock, which would last for months. However, for the time being, Heraclius and his men could march home in peace, assured that the protracted conflict was finished, while the Iranian military could start preparing operations against the Turks in the South Caucasus.[34]

Kavad II soon died of a devastating plague,[23] which became known as the Plague of Sheroe.[35] According to the 10th-century Arab historian and geographer al-Masudi, at least a third of Iran's population—or perhaps even half—died to the plague. Al-Tabari reported that "most of the Persians perished." According to the modern historian Michael Bonner, epidemic sickness would have quickly swept throughout Mesopotamia's crowded and densely populated communities. He adds that while it is possible the highlands of Iran remained unharmed, sources raise the possibility that the plague's impact on Ctesiphon urban area was as devastating as they claim.[23] It is uncertain around what time Kavad II died, as sources differ on whether he ruled six, seven, or eight months. He died in late summer or early autumn,[36] and was succeeded by his seven-year-old son Ardashir III, who was supervised by Mah-Adhur Gushnasp as his regent.[23]