不自量力 — “To overestimate one's own abilities or capabilities”

During the Spring and Autumn period, there were two vassal states, Zheng and Xi, located in what is now Henan Province. In 712 BC, the State of Xi launched a war against the State of Zheng. Although both were small, Xi had significantly less manpower, resources, and military strength than Zheng. Predictably, the war ended in Xi's defeat.

Afterwards, some insightful people predicted that Xi was on the verge of collapse. Their analysis was based on five critical mistakes Xi had made: first, it did not consider its own moral standing; second, it did not assess whether its strength was sufficient for victory; third, it failed to build good relations with friendly neighboring states; fourth, it did not clearly articulate its reasons for attacking Zheng; and fifth, it did not discern who was responsible for its failure.

Committing these five grave errors and still embarking on a military campaign against another state, was it not natural that it would end in defeat? As expected, the State of Xi was soon conquered by the State of Chu.