November 602 · Constantinople Theater

When a mutinous Byzantine army proclaimed the centurion Phocas emperor and marched on Constantinople, the emperor Maurice was overthrown and, with his sons, brutally executed. Khosrow II of Persia — whom Maurice had earlier restored to his throne, making them allies — seized on the murder of his benefactor as a pretext for war, declaring he would avenge Maurice.

611 · Syria Theater

The Persian armies, exploiting Byzantine disarray, poured across the eastern frontier and into Syria, capturing the great city of Antioch — one of the largest in the empire — in 611. The Sasanian tide rolled on toward the Mediterranean coast and the Holy Land.

May 614 · Palestine Theater

After a three-week siege, the Persians stormed Jerusalem. In the sack that followed, tens of thousands of Christians were reportedly killed, churches including the Holy Sepulchre were burned, and — most shocking of all to the Christian world — the relic of the True Cross was carried off in triumph to the Persian capital.

618 – 621 · Egypt Theater

The Persians completed their conquest of the Roman East by overrunning Egypt, taking the great city of Alexandria and the empire's richest province by 621. With Egypt fell the grain supply that fed Constantinople itself.

622 · Cappadocia / Cilicia (Asia Minor) Theater

Having overthrown Phocas and spent years rebuilding the army, Heraclius took the field in person in 622 and, in a campaign in Asia Minor near the old battlefield of Issus, outmanoeuvred and defeated Shahrbaraz's Persian army — the first major Byzantine victory of the war and proof that the tide could be turned.

July – August 626 · Constantinople Theater

With Heraclius and his army far away in the Caucasus, the Persians under Shahrbaraz and their allies the Avars laid siege to Constantinople itself, attacking from both sides of the Bosporus. But the great Theodosian Walls held, the Byzantine navy prevented the Persians and Avars from linking up across the strait, and the defenders — rallied by the Patriarch Sergius around an icon of the Virgin — threw back every assault until the Avars withdrew.

627 · Caucasus and Mesopotamia Theater

In a daring strategic gamble, Heraclius allied with the Göktürks of the steppe, marched through the Caucasus, and drove deep into the Persian heartland from the north — bypassing the Persian field armies to strike at the empire's undefended core, sacking Khosrow's palace at Dastagird and threatening the capital, Ctesiphon.

December 12, 627 · Mesopotamia (near ancient Nineveh) Theater

Near the ruins of ancient Nineveh, Heraclius turned and gave battle to the pursuing Persian army in a dense winter fog. The emperor led from the front, reportedly killing the Persian commander Rhahzadh in single combat, and the Byzantine army destroyed the last major Persian field force in a decisive victory.

628 – 630 · Ctesiphon (Mesopotamia) and Jerusalem Theater

With Persia in ruins, Khosrow II was overthrown and murdered by his own son Kavad II, who at once made peace with Heraclius, withdrawing from all the conquered Roman territories and returning the True Cross. In 630 Heraclius personally carried the relic back to Jerusalem in a triumphal ceremony — the emperor at the summit of his glory.