养虎遗患 — “To keep a tiger as a pet and suffer later”

At the end of the Qin Dynasty, the tyrannical rule of the Qin state provoked widespread rebellion among the people. Liu Bang and Xiang Yu emerged as prominent leaders of these insurgent forces.

Liu Bang was the first to capture Xianyang, the Qin capital, which greatly displeased Xiang Yu, who then resolved to attack Liu Bang. Given Xiang Yu's formidable power at the time, Liu Bang dared not confront him directly and retreated to Hanzhong.

Later, Liu Bang appointed capable officials and implemented benevolent policies, gradually strengthening his forces. Xiang Yu, on the other hand, became increasingly isolated.

At this point, Liu Bang did not launch an attack; instead, he sent envoys to negotiate with Xiang Yu, proposing to establish Honggou as their border, with each occupying one side, and signing a non-aggression pact. Xiang Yu, realizing that he could hardly defeat Liu Bang with his current strength, reluctantly accepted this proposal.

After the agreement was signed, Xiang Yu led his troops eastward, and Liu Bang, feeling satisfied, planned to withdraw his forces westward back to his own territory. However, his ministers, including Zhang Liang, advised him, saying, 'You have already seized most of the land under heaven, and the feudal lords have all pledged allegiance to you. Xiang Yu's army is now vulnerable. If you do not eliminate him now, he will become a future menace – truly raising a tiger to suffer later!' Liu Bang found their counsel very reasonable.

Consequently, he launched an attack, defeated and destroyed Xiang Yu, and established the Western Han Dynasty.