The successful campaign in Georgia had likely…
629 CE
The successful campaign in Georgia had likely encouraged Tong Yabghu to grander designs.
This time, he plans to incorporate Aghvania into his Western Turkic khaganate, rather than to wield a usual campaign of plunder.
Before returning to Suyab, he instructs 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 is eager to retain control of the westernmost portion of the Silk Route, as he tightens his grip of its other segments all the way east to China.
Böri Shad determines to expand his control of Transcaucasia and in April 629 sends the Khazar general Chorpan Tarkhan with as little as thirty thousand cavalry to invade Armenia.
Using a characteristic ploy of nomadic warriors, Chorpan Tarkhan ambushes and annihilates a Persian force of ten thousand dispatched by Shahrbaraz to counter the invasion.
The Turks unexpectedly withdraw of their own accord from Transcaucasia later in 629, but this is more than outweighed by domestic political instability.