In 615, during the Byzantine–Sasanian War of 602–628 with the Sasanian army under spahbod Shahin invaded Asia Minor and reached Chalcedon, across the Bosporus from Constantinople.
It was at this point, according to Sebeos, that Heraclius had agreed to stand down and was about ready to become a client of the Sasanian emperor Khosrow II, allowing the Byzantine Empire to become a client state of the Sasanid Empire, as well as even allow Khosrow II to choose the emperor.
After negotiations with Byzantine Emperor Heraclius, an ambassador was sent to Sasanian Shahanshah Khosrow II, and Shahin withdrew again to Syria.
God and your majesty, have sent [to you] your slaves Olympius the most glorious former consul, the patrician and praetorian prefect, and Leontius the most glorious former consul, patrician and city prefect, and Anastasius the most God-loved presbyter [of Hagia Sophia]; we beseech that they may be received in an appropriate manner by your superabundant Might.a Heraclius sent a separate letter to Shahin, stating his willingness to accept whoever was appointed by the Sasanians as the ruler of Byzantium.
These efforts were failed but the Byzantine capital was not attacked, because the Sasanians preferred to focus on Egypt, which was of higher economic value than the war-torn Anatolia.