The Siege of Tiflis (627-628)

When Constantinople was besieged by the Avars and Sasanians in 626, the Byzantine emperor Heraclius looked for allies. He sent an envoy to the steppe and made an alliance with Tong Yabghu, khagan of the Western Turks, who appears in Byzantine sources as "Ziebel".

In 627 the Turkic army came south along the Caspian shore, took the pass of Derbent and crossed Albania, today's Azerbaijan. Near Tiflis they met Heraclius, who gave the Turkic ruler his own crown. The allies besieged Tiflis, but the city held out for a long time; according to the Albanian historian Movses Kaghankatvatsi, the defenders mocked the Turkic ruler from the walls.

Heraclius went on into Iran and defeated the Sasanians at Nineveh in December 627, while the Turks took Tiflis in 628. The campaign was one of the last blows that broke Sasanian Iran, which fell to the Arabs a few years later.