高屋建瓴 — “To be in a commanding or strategically advantageous position”

During the Chu-Han Contention, Han Xin, a great general under King Liu Bang of Han, achieved numerous military successes. He became conceited due to his achievements. After pacifying the Qi region, he wrote to Liu Bang, requesting to be appointed "acting King of Qi." Liu Bang was furious, dismissing Han Xin's request as a pipe dream. Zhang Liang, one of Liu Bang's advisors, after reading the letter, persuaded him, "Currently, our side is at a disadvantage, the Chu army is still strong, and Han Xin commands a significant portion of our forces. Your Majesty might as well go along with his request." Liu Bang understood, and sent Zhang Liang as a special envoy with the royal seal to enfeoff Han Xin as King of Qi.

Han Xin was very pleased and promised to quickly dispatch troops to attack King Xiang Yu of Chu. The Han army set up an ambush at Gaixia, with Han Xin leading the three armies and Liu Bang guarding the main camp. Han Xin, being both brave and resourceful, defeated King Xiang Yu, who then committed suicide with his sword. Liu Bang, concerned about Han Xin's high position and power, stripped him of his military command, took back the Qi territory, and re-enfeoffed him as King of Chu. In 202 BC, Liu Bang became emperor, known as Emperor Gaozu of Han.

Soon after, someone accused Han Xin of harboring Xiang Yu's former general, Zhong Limao, suggesting Han Xin was planning a rebellion. When this news reached Han Xin, some advised him, "Why not kill Zhong Limao to show your loyalty and please the Emperor?" Han Xin replied, "Zhong Limao and I have always been friends. When I was in the Chu camp, King Xiang Yu once wanted to kill me, and it was Zhong Limao who saved me. Now that he has nowhere to go, how could I bear to kill him?" Despite saying this, Han Xin eventually spoke to Zhong Limao directly about the matter. Zhong Limao, seeing through his intentions, cursed him for his ingratitude and committed suicide. Subsequently, Han Xin presented Zhong Limao's head to Liu Bang.

Still suspicious of Han Xin's sincerity, Liu Bang ordered his warriors to bind him. Upon hearing this, Grand Master Tian Ken sought an audience with Liu Bang, saying, "There are several things worth congratulating Your Majesty on. Firstly, Han Xin has been captured; secondly, Your Majesty firmly controls San Qin (the Guanzhong region). Your Majesty can use this strategically advantageous terrain to control and command the feudal lords, just like pouring water from a bottle off a high roof." Tian Ken continued, "The Qi region, spanning over two thousand li and seventy cities, is extremely important; controlling it allows one to contend against ten. Such an important place cannot be entrusted to anyone but one's own children." Liu Bang understood that Tian Ken was subtly pleading for Han Xin. After all, pacifying San Qin and Qi was primarily Han Xin's achievement. Thus, Liu Bang pardoned Han Xin, merely demoting him to Marquis of Huaiyin.