Smbat is first mentioned some time in the 580s, when the emperor Maurice requested the Armenian nobles to raise cavalry for service in his wars against the Avars.
Smbat and Sahak Mamikonian led a thousand-strong unit each to Constantinople, where they were richly rewarded and sent home.
Sebeos also adds that Maurice supposedly adopted Smbat at this occasion.
In 589, however, Smbat led a rebellion against the Empire, was captured and sent to Constantinople, where he was condemned to death and was thrown to be devoured by the beasts in the Hippodrome of Constantinople.
He was pardoned at the last minute by Maurice, who then banished him to some "distant islands" and later to Africa.
Smbat returned from exile some time after, and entered the service of the Sasanian shah Khosrow II, who in 595 had appointed him marzban (military governor) of Hyrcania (the southern coastlands of the Caspian Sea).
Smbat had served in this post until 602, but was initially employed in suppressing the rebellion of Vistahm in Khorasan, before being recalled to reside at the royal court in Ctesiphon.
There he had received further honors, and been appointed Lesser Minister of Finance.
In about 607 ("the eighteenth year of Khosrow's reign") he is sent back to Armenia with extensive powers as "Commander of the army of the lords of houses".
His tenure in Armenia is short but productive.
Smbat receives the honorific title Khosrow Shun ("the Joy or Satisfaction of Khosrow") in the next year, and leads a campaign around this time on behalf of Khosrow against the Hephthalites.
