According to a Syriac source, echoed in the Chronicle of Theophanes the Confessor, Kardarigan's forces are said to have seized many cities, conquered Armenia, and marched through Cappadocia, Galatia, and Paphlagonia reaching Chalcedon, across from the Byzantine capital of Constantinople in 608 or 609.
[3][4] Kardarigan re-appears in 626 as the second-in-command of the Persian army under Shahrbaraz, sent to take part in the joint siege of Constantinople with the Avars.
The destruction by the Byzantines of the fleet of the Avars' Slavic subjects forced the Persians into a passive role in the siege, which was repulsed.
At this juncture, Khosrau sent a letter to him, ordering him to kill Shahrbaraz, assume command of the army, and return it to Persia.
In 629, however, after Khosrau's overthrow, Shahrbaraz killed the legitimate shah, the boy ruler Ardashir III (r. 628–629) and assumed the throne himself.