Han Xin, a founding general of Emperor Gaozu Liu Bang, had led armies across the land and earned countless victories. After Liu Bang declared himself emperor, he stripped Han Xin of his military command and enfeoffed him as the King of Chu.
The following year, someone secretly reported to Liu Bang that Han Xin was hiding Xiang Yu's general Zhongli Mei in his home and might be plotting rebellion. Though Liu Bang knew Han Xin would never rebel, he seized this excuse to eliminate him, so he pretended to tour the Yunmeng Marsh and sent messengers ordering all feudal lords to gather at Chen City, planning to arrest and charge Han Xin when he arrived.
When the regional lords arrived, Han Xin was nowhere to be seen. He had received the summons but sensed something was amiss and hesitated to go. Someone advised him, "Kill Zhongli Mei to prove your loyalty to Liu Bang." Zhongli Mei had once saved Han Xin's life, and Han Xin initially could not bear it. But to protect his own title, he forced Zhongli Mei to commit suicide, then brought the severed head to Yunmeng Marsh to pay homage to Liu Bang.
But Liu Bang did not forgive Han Xin for this. He ordered his guards to seize Han Xin and take him back to the capital. Minister Tian Ken, sensing Liu Bang's intent to kill Han Xin, said to the emperor, "Your Majesty has captured Han Xin and now firmly controls the Guanzhong region. Guanzhong is vast, strategically fortified, and boasts strong troops and horses. If you were to march against the feudal lords, it would be like pouring water from a steep roof—an unstoppable force. As for the Qi region, it stretches over 2,000 li with more than 70 cities, holding immense strategic importance. With Qi, 200,000 men can resist a million enemy troops. That is why Qi and Guanzhong have long been called the Three Qins. From now on, unless it is Your Majesty's own son or brother, no one else should be appointed as the King of Qi!"
Emperor Liu Bang understood that Tian Ken was subtly pleading for Han Xin's life. After all, it was Han Xin who had pacified both the Qin and Qi territories, earning undeniable merit. Since Han Xin had not actually rebelled, executing him rashly could breed suspicion among other feudal lords and destabilize the regime.
After careful deliberation and weighing the pros and cons, Emperor Liu Bang demoted Han Xin to the Marquis of Huaiyin, using the excuse that Han Xin had harbored the fugitive general Zhongli Mei.
Later, the idiom "Pouring Water from a High Roof" came to mean commanding a position of superiority with irresistible force.
Source: *Records of the Grand Historian*, Chapter "Annals of Gaozu"
Meaning of the Idiom: Later, the Chinese idiom "高屋建瓴" came to describe commanding a position of superiority with irresistible force.