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.

[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 Sassanid Persia.

Lev Gumilev observes that the lightly armed militia of Aghvania was no match against the hordes of heavy cavalry led by Tong Yabghu.

The fall and sack of Derbent were described in detail by the Armenian historian Movses Kagankatvatsi, thought to have been an eyewitness to the event: At the arrival of the all-powerful scourge (universal wrath) confronting us, the invaders [Turks], like billowing waves of the sea, crashed against the walls and demolished them to their foundations.

[In Partaw], seeing the terrible danger from the multitude of hideously ugly, vile, broad-faced, without eyelashes, and with long flowing hair like women, which descended upon them, a great terror (trembling) seized the inhabitants.

Their eyes had no mercy for neither the beautiful, nor handsome, nor the young men or women; they did not spare even the unfit, harmless, lame, nor old; they had no pity (compassion, regrets), and their hearts did not shrink at the sight of the babies embracing their murdered mothers; to the contrary, they suckled blood from their breasts like milk.

In the words of Movses Kagankatvatsi, the Khazars "encircled and besieged the famous and great sybaritic trade city of Tbilisi,"[11] whereupon they were joined by Emperor Heraclius with his mighty army.

[12] 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.

[14] 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 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".

[18] 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.