Northern and Southern States period
The Northern and Southern States period (698–926) is the period in Korean history when Unified Silla and Balhae coexisted in the south and north of the peninsula. == Historiography == The Northern and Southern States period is a historical paradigm born out of advocacy for a Korean identity for Balhae and to incorporate it as an integral part of Korean history.
Source: Wikipedia — Northern and Southern States period (CC BY-SA 4.0)