In 615, during the ongoing war with the Byzantine Empire, 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 Roman Empire to become a Persian client state, as well as even allow Khosrow II to choose the emperor. The Sassanids had already captured Roman Syria and Palestine in the previous year. After negotiations with Byzantine Emperor Heraclius, a Byzantine ambassador was sent to Persian Shahanshah Khosrau II, and Shahin withdrew again to Syria.