In 615, during the ongoing war with the East Roman (Byzantine) Empire, the Sassanid Persian

Sassanid Empire

The Sassanid Empire , known to its inhabitants as Ērānshahr and Ērān in Middle Persian and resulting in the New Persian terms Iranshahr and Iran , was the last pre-Islamic Persian Empire, ruled by the Sasanian Dynasty from 224 to 651...

 army under spahbod

Spahbod

Spahbod or Spahbed , is derived from the words Spah and bod ; or "Aspah'Paeity" , and means commander of cavaliers/ knights; alternatively Spah Salar was a rank used in the Parthian empire and more widely in the Sassanid Empire of Persia...

 Shahin invaded Asia Minor

Asia Minor

Asia Minor is a geographical location at the westernmost protrusion of Asia, also called Anatolia, and corresponds to the western two thirds of the Asian part of Turkey...

 and reached Chalcedon

Chalcedon

Chalcedon , sometimes transliterated as Chalkedon) was an ancient maritime town of Bithynia, in Asia Minor, almost directly opposite Byzantium, south of Scutari . It is now a district of the city of Istanbul named Kadıköy...

, across the Bosporus from Constantinople

Constantinople

Constantinople was the capital of the Roman, Eastern Roman, Byzantine, Latin, and Ottoman Empires. Throughout most of the Middle Ages, Constantinople was Europe's largest and wealthiest city.-Names:...

. The Sassanids had already captured Roman Syria and Palestine in the previous year. After negotiations with Byzantine Emperor Heraclius

Heraclius

Heraclius was Byzantine Emperor from 610 to 641.He was responsible for introducing Greek as the empire's official language. His rise to power began in 608, when he and his father, Heraclius the Elder, the exarch of Africa, successfully led a revolt against the unpopular usurper Phocas.Heraclius'...

, a Byzantine ambassador was sent to Persian Shahanshah Khosrau II

Khosrau II

250px|thumb|Khosrau II 250px|thumb|Khosrau II 250px|thumb|Khosrau II (Khosrow II, Chosroes II, or Xosrov II in classical sources, sometimes called Parvez, "the Ever Victorious" – (in Persian: خسرو پرویز), was the twenty-second Sassanid King of Persia, reigning from 590 to 628...

, and Shahin withdrew again to Syria.