Battle of Nineveh ( 627 ) The Battle of Nineveh " ( Ἡ μάχη τῆς Νινευί ) " was the climactic battle of the Byzantine - Sassanid War of 602 – 628 . The Byzantine victory later resulted in civil war in Persia and for a period of time restored the empire to its ancient boundaries in the Middle East . This resurgence of power and prestige was not to last , however , as within a matter of decades an Arab Caliphate emerged from Arabia and once again brought the empire to the brink of destruction . Prelude . When Emperor Maurice was murdered by the usurper Phocas , Khosrau II declared war , ostensibly to avenge his benefactor ' s death . While the Persians proved largely successful during the first stages of the war , conquering much of the Levant , Egypt , and even Anatolia , the ascendancy of Heraclius eventually led to the Persians ' downfall . Heraclius ' campaigns altered the balance , forcing the Persians on the defensive and allowing for the Byzantines to regain momentum . Allied with the Avars , the Persians attempted to take Constantinople , but were defeated there . While the Siege of Constantinople was taking place , Heraclius allied with what Byzantine sources called the Khazars under Ziebel , who are identified with the Western Turkic Khaganate of the Göktürks led by Tong Yabghu , plying him with wondrous gifts and a promise of the reward of the porphyrogenita Eudoxia Epiphania . The Caucasus - based Turks responded by sending 40 , 000 of their men to ravage the Persian empire in 626 to start the Third Perso - Turkic War . Joint Byzantine and Göktürks operations were focused on besieging Tiflis . Invasion of Mesopotamia . In mid - September 627 , leaving Ziebel to continue the siege of Tiflis , Heraclius invaded the Persian heartland , this time with between 25 , 000 and 50 , 000 troops and 40 , 000 Göktürks . The Göktürks , however , quickly deserted him because of the strange winter conditions . Heraclius was tailed by Rhahzadh ' s army of 12 , 000 , but managed to evade Rhahzadh and invaded the heartland of the Persian Empire , in Mesopotamia ( modern Iraq ) . Heraclius acquired food and fodder from the countryside , so Rhahzadh , following through countryside already stripped , could not easily find provisions . This resulted in harm to Rhahzadh ' s animals . On 1 December , Heraclius crossed the Great Zab River and camped near the ruins of the capital of the former Assyrian Empire of Nineveh in Persian ruled Assyria / Assuristan . This was a movement from south to north , contrary to the expectation of a southward advance . However , this can be seen as a way to avoid being trapped by the Persian army in case of a defeat . Rhahzadh approached Nineveh from a different position . News that 3 , 000 Persian reinforcements were approaching reached Heraclius , forcing him to act . He gave the appearance of retreating from Persia by crossing the Tigris . Field . Heraclius had found a plain west of the Great Zab some distance from the ruins of Nineveh . This allowed the Byzantines to take advantage of their strengths in lances and hand - to - hand combat . Furthermore , the fog reduced the Persian advantage in missile troops and allowing the Byzantines to charge without great losses from missile barrages . Walter Kaegi believes that this battle took place near the Karamlays Creek . The battle . Rhahzadh deployed his forces into three masses and attacked . Heraclius feigned retreat to lead the Persians to the plains before reversing his troops to the surprise of the Persians . After eight hours of fighting , the Persians suddenly retreated to nearby foothills , but it was not a rout . 6 , 000 Persians fell . Nikephoros ' " Brief History " tells that Rhahzadh challenged Heraclius to personal combat . Heraclius accepted and killed Rhahzadh in a single thrust ; two other challengers fought and also lost . In any case , Rhahzadh died sometime in the battle . The 3 , 000 Persian reinforcements arrived too late for the battle . Aftermath . The victory at Nineveh was not total as the Byzantines were unable to capture the Persian camp . However , this victory was significant enough to shatter the resistance of the Persians . With no Persian army left to oppose him , Heraclius ' victorious army plundered Dastagird , Khosrau ' s palace , and gained tremendous riches while recovering 300 captured Byzantine / Roman standards accumulated over years of warfare . Khosrau had already fled to the mountains of Susiana to try to rally support for the defense of Ctesiphon . Heraclius could not attack Ctesiphon itself because the Nahrawan Canal was blocked by the collapse of a bridge . The Persian army rebelled and overthrew Khosrau II , raising his son Kavadh II , also known as Siroes , in his stead . Khosrau perished in a dungeon after suffering for five days on bare sustenance — he was shot to death slowly with arrows on the fifth day . Kavadh immediately sent peace offers to Heraclius . Heraclius did not impose harsh terms , knowing that his own empire was also near exhaustion . Under the peace treaty , the Byzantines regained all their lost territories , their captured soldiers , a war indemnity , and of great spiritual significance , the True Cross and other relics that were lost in Jerusalem in 614 . The battle marked the end of the Roman - Persian Wars .