page_title: Byzantine–Sasanian War of 602–628
section_title: Siege of Constantinople
hierarchical_section_title: Byzantine–Sasanian War of 602–628 / Climax of the war / Siege of Constantinople
caption_attribution_description: English: Cherub (of Ezekiel vision, not putto) and Byzantine Emperor Heraclius receiving the submission of the Sassanid king Khosrau II; plaque from a cross. Champlevé enamel over gilt copper, 1160-1170, Meuse Valley. Français&#160;: Chérubin et l'empereur byzantin Héraclius soumettant le roi sassanide Khosro II, plaque provenant d'une croix. Émail champlevé sur cuivre doré, 1160-1170, vallée de la Meuse.
context_page_description: The Byzantine–Sasanian War of 602–628 was the final and most devastating of the series of wars fought between the Byzantine Empire and the Sasanian Empire of Iran. The previous war between the two powers had ended in 591 after Emperor Maurice helped the Sasanian king Khosrow II regain his throne. In 602 Maurice was murdered by his political rival Phocas. Khosrow proceeded to declare war, ostensibly to avenge the death of Maurice. This became a decades-long conflict, the longest war in the series, and was fought throughout the Middle East: in Egypt, the Levant, Mesopotamia, the Caucasus, Anatolia, Armenia, the Aegean Sea and before the walls of Constantinople itself.
  While the Persians proved largely successful during the first stage of the war from 602 to 622, conquering much of the Levant, Egypt, several islands in the Aegean Sea and parts of Anatolia, the ascendancy of emperor Heraclius in 610 led, despite initial setbacks, to a status quo ante bellum. Heraclius' campaigns in Iranian lands from 622 to 626 forced the Persians onto the defensive, allowing his forces to regain momentum.
context_section_description: Khosrow, seeing that a decisive counterattack was needed to defeat the Byzantines, recruited two new armies from all the able men, including foreigners. Shahin was entrusted with 50,000 men and stayed in Mesopotamia and Armenia to prevent Heraclius from invading Iran; a smaller army under Shahrbaraz slipped through Heraclius' flanks and bee-lined for Chalcedon, the Persian base across the Bosphorus from Constantinople. Khosrow also coordinated with the Khagan of the Avars so as to launch a coordinated attack on Constantinople from both European and Asiatic sides. The Persian army stationed themselves at Chalcedon, while the Avars placed themselves on the European side of Constantinople and destroyed the Aqueduct of Valens. Because of the Byzantine navy's control of the Bosphorus strait, however, the Persians could not send troops to the European side to aid their ally. This reduced the effectiveness of the siege, because the Persians were experts in siege warfare. Furthermore, the Persians and Avars had difficulties communicating across the guarded Bosphorus—though undoubtedly, there was some communication between the two forces.
  The defense of Constantinople was under the command of Patriarch Sergius and the patrician Bonus. Upon hearing the news, Heraclius split his army into three parts; although he judged that the capital was relatively safe, he still sent some reinforcements to Constantinople to boost the morale of the defenders. Another part of the army was under the command of his brother Theodore and was sent to deal with Shahin, while the third and smallest part would remain under his own control, intending to raid the Persian heartland.
  On 29 June 626, a coordinated assault on the walls began. Inside the walls, some 12,000 well-trained Byzantine cavalry troops (presumably dismounted) defended the city against the forces of some 80,000 Avars and Slavs. Despite continuous bombardment for a month, morale was high inside the walls of Constantinople because of Patriarch Sergius' religious fervor and his processions along the wall with the icon of the Virgin Mary, inspiring the belief that the Byzantines were under divine protection.
  On 7 August, a fleet of Persian rafts ferrying troops across the Bosphorus were surrounded and destroyed by Byzantine ships. The Slavs under the Avars attempted to attack the sea walls from across the Golden Horn, while the main Avar host attacked the land walls. Patrician Bonus' galleys rammed and destroyed the Slavic boats; the Avar land assault from August 6 to the 7th also failed. With the news that Theodore had decisively triumphed over Shahin (supposedly leading Shahin to die from depression), the Avars retreated to the Balkan hinterland within two days, never to seriously threaten Constantinople again. Even though the army of Shahrbaraz was still encamped at Chalcedon, the threat to Constantinople was over. In thanks for the lifting of the siege and the supposed divine protection of the Virgin Mary, the celebrated Akathist Hymn was written by an unknown author, possibly Patriarch Sergius or George of Pisidia.
  Furthermore, after the emperor showed Shahrbaraz intercepted letters from Khosrow ordering the Persian general's death, the latter switched to Heraclius' side. Shahrbaraz then moved his army to northern Syria, where he could easily decide to support either Khosrow or Heraclius at a moment's notice. Still, with the neutralization of Khosrow's most skilled general, Heraclius deprived his enemy of some of his best and most experienced troops, while securing his flanks prior to his invasion of Iran.
caption: Cherub and Heraclius receiving the submission of Khosrow II; plaque from a cross (Champlevé enamel over gilt copper, 1160-1170, Louvre, Paris). This is only an allegory, since Khosrow never submitted in person to Heraclius.
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