Editing Shahrbaraz (section)

== Siege of Constantinople ==
{{main|Siege of Constantinople (626)}}
Shahrbaraz, along with a smaller army, later managed to slip through Heraclius' flanks and bee-lined for [[Chalcedon]], the Sasanian base across the [[Bosphorus]] from [[Constantinople]]. Khosrow II coordinated with the [[Khagan]] of the [[Pannonian Avars|Avars]] so as to launch a coordinated attack on Constantinople from both European and Asiatic sides.<ref name = "Oman210" /> The army of Shahrbaraz stationed themselves at Chalcedon, while the Avars placed themselves on the European side of Constantinople and destroyed the [[Valens Aqueduct|Aqueduct of Valens]].<ref>{{Harvnb|Treadgold|1997|p=[https://books.google.com/books?id=nYbnr5XVbzUC&pg=PA297 297]}}</ref> Because of the [[Byzantine navy]]'s control of the Bosphorus strait, however, the Sasanians could not send troops to the European side to aid their ally.<ref>{{Harvnb|Kaegi|2003|p=133}}</ref><ref name="Kaegi140">{{Harvnb|Kaegi|2003|p=140}}</ref> This reduced the effectiveness of the siege, because the Sasanians were experts in siege warfare.<ref name="frontier179">{{Harvnb|Dodgeon|Greatrex|Lieu|2002b|pp=179–181}}</ref> Furthermore, the [[Sasanians]] and Avars had difficulties communicating across the guarded Bosphorus—though undoubtedly, there was some communication between the two forces.<ref name = "Oman210" /><ref name="Kaegi140" /><ref>{{Harvnb|Kaegi|2003|p=134}}</ref>
[[File:Constantinople area map.svg|300px|thumb|Map of the environs of Constantinople in Byzantine times.]]
On 7 August, a fleet of Sasanian rafts ferrying troops across the Bosphorus was 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 6 to 7 August also failed.<ref>{{Harvnb|Kaegi|2003|p=137}}</ref> 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 threaten Constantinople seriously again. Even though the army of Shahrbaraz was still encamped at Chalcedon, the threat to Constantinople was over.<ref name = "Oman211">{{Harvnb|Oman|1893|p=[https://books.google.com/books?id=N6A-AAAAYAAJ&pg=PA211 211]}}</ref><ref name="Norwich93">{{Harvnb|Norwich|1997|p=93}}</ref>

Disappointed by Shahrbaraz's failure, Khosrow II sent a messenger bearing a letter to [[Kardarigan (7th century)|Kardarigan]], who was the second-in-command of the Sasanian army. The letter said that Kardarigan should kill Shahrbaraz and take his army back to [[Ctesiphon]], but the bearers of the letter were intercepted in [[Galatia]] by Byzantine soldiers, who gave the letter to the future emperor [[Constantine III (Byzantine emperor)|Constantine III]] who in turn gave it to Heraclius. After reading the letter, he offered to show the letter to Shahrbaraz in a meeting at Constantinople. Shahrbaraz accepted his proposal and met Heraclius at Constantinople, where he read the letter and switched over to Heraclius' side.<ref>{{Harvnb|Kaegi|2003|p=148}}</ref> Shahrbaraz then changed the contents of the letter, making it state that Khosrow II wanted 400 officers killed, ensuring that Kardarigan and the rest of the army remained loyal to him.<ref name="frontier171">{{Harvnb|Dodgeon|Greatrex|Lieu|2002b|p=205}}</ref>

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]].<ref>{{Harvnb|Kaegi|2003|p=151}}</ref>