During the siege of Constantinople, Heraclius formed an alliance with people Byzantine sources called the "Khazars", under Tong Yabghu Qaghan, now generally identified as the Western Turkic Khaganate of the Göktürks,[1] plying him with wondrous gifts and the promise of marriage to the porphyrogenita Eudoxia Epiphania.

[2] Istämi sent an embassy led by the Sogdian diplomat Maniah directly to Constantinople, which arrived in 568 and offered not only silk as a gift to Justin II, but also proposed an alliance against Sasanian Iran.

By the time of Vezhan Buzmihr's tenure as marzban of Iberia, the hagiographies of the period implied that the "kings" in Tbilisi had only the status of mamasakhlisi, which means "head of the (royal) house".

[13] 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.

[14] On December 12, he defeated the Sasanids in the Battle of Nineveh and marched to Ctesiphon, but before reaching the capital, Khosrow II was killed by his son Kavad, and in April 628 he made a truce with Heraclius.