Since the reign of Adarnase IV, the powerful neighbouring Kingdom of Abkhazia had extended its influence into Inner Georgia and even reduced the local kings to the status of vassals.

This made King Sumbat a vassal of George II of Abkhazia, who had to submit to the orders of the Abkhazian viceroy of Iberia, Leon.

It was under his reign that Iberia went to war against Kakheti on several occasions during campaigns that failed to produce any decisive results; however, there is no evidence of Sumbat's involvement in these battles.

[3] However, he was unable to hold this position for very long, dying in 958, leaving his throne to his eldest son Bagrat II.

Sumbat is commemorated in the church inscriptions from Ishkhani and Doliskana in what is now Artvin Province, Turkey.