Third Perso - Turkic War The Third Perso - Turkic War was the third and final conflict between the Sassanian Empire and the Western Turkic Khaganate . Unlike the previous two wars , it was not fought in Central Asia , but in Transcaucasia . Hostilities were initiated in 627 AD by Khagan Tong Yabghu of the Western Göktürks and Emperor Heraclius of the Eastern Roman Empire . Opposing them were the Sassanid Persians , allied with the Eurasian Avars . The war was fought against the background of the last Byzantine - Sassanid War and served as a prelude to the dramatic events that changed the balance of powers in the Middle East for centuries to come ( Battle of Nineveh , Islamic conquest of Persia ) . Background . Following the First Siege of Constantinople by the Avars and Persians , the beleaguered Byzantine Emperor Heraclius found himself politically isolated . He could not rely on the Christian Armenian potentates of Transcaucasia , since they were branded as heretics by the Orthodox Church , and even the king of Iberia preferred to befriend the religiously tolerant Persians . Against this dismal background , he found a natural ally in Tong Yabghu . Earlier in 568 , the Turks under Istämi had turned to Byzantium when their relations with Persia soured over commerce issues . In 625 , Heraclius dispatched to the steppes his emissary , named Andrew , who promised to the Khagan some " staggering riches " in return for military aid . The khagan , on his part , was anxious to secure the Chinese - Byzantine trade along the Silk Route , which had been disrupted by the Persians in the aftermath of the Second Perso - Turkic War . He sent word to the Emperor that " I shall take revenge on your enemies and will come with my valiant troops to your help " . A unit of 1 , 000 horsemen fought their way through Persian Transcaucasia and delivered the Khagan ' s message to the Byzantine camp in Anatolia . Siege of Derbent . Early in 627 , the Göktürks and their Khazar allies approached the Caspian Gates at Derbent . This newly built stronghold was the only gate to the fertile land of Aghvania ( modern - day Azerbaijan ) . Lev Gumilev observes that the lightly armed militia of Aghvania was no match against the hordes of heavy cavalry led by Tong Yabghu . His troops stormed Derbent and swarmed over Aghvania , plundering it thoroughly . The fall and sack of Derbent was described in detail by the Armenian historian Movses Kagankatvatsi , thought to have been an eyewitness to the event : The fall of the fortress that had been considered impregnable sparked panic all over the country . Aghvanian forces withdrew to their capital , Partav , from whence they made for the Caucasus Mountains . The Göktürks and Khazars overtook them near the village of Kalankatuyk , where they were either slain or taken prisoner . The conquerors imposed upon Aghvania a heavy system of taxation , as reported by Movses : Siege of Tbilisi . The next objective of the Turkic - Byzantine offensive was the Kingdom of Iberia , whose ruler Stephanus was a tributary to Khosrau II of Persia . In the words of Movses Kagankatvatsi , the Khazars " encircled and besieged the famous and great sybaritic trade city of Tbilisi , " whereupon they were joined by Emperor Heraclius with his mighty army . Heraclius and Tong Yabghu ( called Ziebel in the Byzantine sources ) met under the walls of Narikala . The yabgu rode up to the emperor , kissed his shoulder and made a bow . In return , Heraclius hugged the barbarian ruler , called him his son , and crowned him with his own diadem . During the ensuing feast the Khazar leaders received ample gifts in the shape of earrings and clothes , while the yabghu was promised the hand of the emperor ' s daughter , Eudoxia Epiphania . The siege dragged on without much progress , punctuated by frequent sallies on the part of the besieged ; one of these claimed the life of their king . After two months the Khazars retreated to the steppe , promising to return by the autumn . Tong Yabghu left young Böri Shad , either his son or nephew , in charge of the remaining forty thousand which were to assist Heraclius during the siege . Before long these departed as well , leaving the Byzantines to continue the siege alone and prompting jeers from the besieged . When the Georgians ironically referred to the Emperor as " the goat , " hinting at his incestuous marriage , Heraclius recalled a passage from the Book of Daniel about the two - horned ram overthrown by the one - horned goat . He interpreted this as a good sign and struck southward against Persia . On 12 December 627 he appeared on the bank of the Tigris and clashed with Persian forces near the ruins of Nineveh . In January he ravaged the environs of the Persian capital Ctesiphon , signalling a sea - change in the Persian - Byzantine relations . Conclusion . After the triumph of Heraclius , Tong Yabghu hastened to resume the siege of Tiflis and successfully stormed the city in winter . " With their swords raised , they advanced on the walls , and all this multitude , climbing upon each other ' s shoulders , rose up the walls . A black shadow fell upon the wobegone citizens ; they were vanquished and lost their ground , " Movses narrates . Although the Georgians surrendered without further resistance , the city was looted and its citizens were massacred . The Persian governor and the Georgian prince were tortured to death in the presence of Tong Yabghu . The Gokturks , renowned for their expertise in hand - to - hand combat , never excelled in siegecraft . For this reason Gumilev attributes the taking of Tiflis to the Khazars . There are good reasons for believing that this success encouraged Tong Yabghu to grander designs . This time he planned to incorporate Aghvania into his khaganate , rather than to wield a usual campaign of plunder . Before returning to Suyab he instructed Böri Shad and his generals to " spare the lives of the rulers and nobles of that land , in as much as they come out to meet my son , surrender to my rule , concede their towns , castles , and trade to my troops " . These words indicate that Tong Yabghu was eager to retain control of the westernmost portion of the Silk Route , as he tightened his grip of its other segments all the way east to China . In April 629 Böri Shad determined to expand his control of Transcaucasia and sent his general Chorpan Tarkhan with as little as 30 , 000 cavalry to invade Armenia . Using a characteristic ploy of nomadic warriors , Chorpan Tarkhan ambushed and annihilated a Persian force of 10 , 000 dispatched by Shahrbaraz to counter the invasion . The Turks later unexpectedly withdrew of their own accord from Transcaucasia in 629 , but this was more than outweighed by domestic political instability .