After Phocas seized power in Constantinople and Emperor Maurice was killed, the Sasanian shah Khosrow II used Maurice’s death as a pretext to renew war against Byzantium, beginning the long 602–628 conflict.
The fortified frontier city of Dara—key to Roman defense in northern Mesopotamia—fell to a Sasanian siege, signaling the effectiveness of Persian offensives early in the war.
A Persian raid under Shahin pushed across Anatolia to Chalcedon, directly opposite Constantinople, demonstrating how far the Sasanians could penetrate while Byzantium was destabilized by internal conflict.
Heraclius entered Constantinople, executed Phocas, and became emperor, inheriting a collapsing eastern front and beginning the political and military reorganization that later enabled Byzantine recovery.
Sasanian forces captured Caesarea (Cappadocia). A year-long Byzantine blockade/siege forced the Persians to break out, but the city was ultimately recovered—an early sign of Heraclius’ efforts to restore control in Anatolia.
Heraclius’ attempt to halt the Persian advance in Syria failed outside Antioch; the defeat helped secure Sasanian control and opened the way for deeper Persian expansion in the Levant.
Persian forces captured Jerusalem after a siege, deported large numbers of captives, and removed major Christian relics—including the True Cross—to Ctesiphon, creating a profound ideological and political shock for Byzantium.
Sasanian forces took Alexandria (a pivotal step in the campaign), and over the next few years extended control up the Nile, bringing the empire’s grain-rich province of Egypt under Persian occupation.
Heraclius initiated a new strategic phase by campaigning in Asia Minor/Caucasus regions; the victory at Mount Ophlimus was among the early successes that restored Byzantine morale and shifted momentum.
Heraclius departed Constantinople to strike into the Sasanian interior via Armenia, deliberately shifting from defense to deep raids designed to force Persian armies onto the defensive and disrupt royal resources.
In Cilicia, Heraclius fought Shahrbaraz near the Sarus River, disrupting Persian maneuvering in Anatolia and contributing to the broader Byzantine operational recovery.
A coordinated assault by the Avars (on the European side) and Persians (at Chalcedon) could not overcome Byzantine naval control of the Bosporus; the siege’s failure removed the immediate existential threat to the capital.
Heraclius’ winter campaign culminated in a decisive victory near Nineveh, breaking organized Persian resistance and accelerating political collapse around Khosrow II.
Following military crisis and elite revolt, Khosrow II was deposed and killed; his son Kavad II (Siroes) quickly opened negotiations, aiming to end the war and stabilize a fractured Sasanian state.
The 628 peace ended the conflict on broadly status quo ante bellum terms, with Persia agreeing to evacuate conquered provinces and return captives and major relics, reversing the dramatic territorial losses of 602–622.
In a highly symbolic postwar act, Heraclius brought the True Cross back to Jerusalem, reinforcing imperial legitimacy and the religious meaning attached to victory in the long war.
Byzantine–Sassanian War (602–628)
