Investigation of when the capital of the Bohai state was relocated to Shangjing City: Evidence from a neglected chronological pottery sherd

The Bohai state (AD 698-926AD) moved its capital four times, but determining the specific timing of the relocation to the second capital has become a controversial historical issue. Recent archaeological discoveries such as the Yanbian border walls indicate that the earliest capital of the Bohai state should be located in the Yanji Basin. Built in the early years of the Bohai state, the Yanbian border walls were erected to defend against the unconquered northern Sumomohe people. These walls were gradually abandoned after the capital was moved to Shangjing City. Pottery sherds marked with the gan zhi year of “Bing-Shen” found in a site similar to the beacon tower on the border walls of Yanbian, as well as the historical background of Bohai state, allow us to speculate that the movement to the Shangjing City capital was in AD 756.