 The Qing historian Wang Fuzhi (1619–1692) wrote that this period can be compared to the earlier Warring States period of ancient China, remarking that none of the rulers could be described as "Son of Heaven".These rulers, despite claiming the status of emperor, sometimes dealt with each other on terms of diplomatic equality out of pragmatic concern.This concept of "sharing the Mandate of Heaven" as "sibling states" was the result of the brief balance of power.