Byzantine-Sasanian War of 602 to 628

The last great war between the Roman (Byzantine) and Persian empires began in 602, when the Persian shah Khosrow II used the murder of the Byzantine emperor Maurice by the usurper Phocas as a reason to invade. Maurice had helped Khosrow win his throne, and the shah claimed to avenge him. The Persians took the fortresses of Mesopotamia and Armenia, and then moved west with astonishing speed. They captured Antioch in 613, Jerusalem in 614, where they took the True Cross, and Egypt by about 619.¹

The two empires had been rivals for centuries, with Rome's capital at Constantinople and Persia ruled by the Sasanian dynasty, and they had fought repeatedly over Armenia, Mesopotamia and the trade routes. A long peace had held under Maurice, but his overthrow in a military revolt gave Khosrow his opportunity. By 626 a Persian army reached the Bosphorus across from Constantinople and, together with the Avars, besieged the city, which held out. The emperor Heraclius, who took power in 610, led a daring counterattack through Armenia and into Persia, and defeated the Persian army at Nineveh in December 627.¹²

Khosrow was overthrown and killed in early 628 by his own nobles, and the new ruler made peace, returning the lost provinces and the True Cross, which Heraclius restored to Jerusalem in 630. But both empires had been bled white. They had lost huge numbers of men, their treasuries were empty, and their frontier provinces were ravaged. Within a few years Arab armies from the new caliphate struck both, taking Syria and Egypt from the Byzantines and conquering the Sasanian Empire entirely by 651.¹²