After establishing the Han Dynasty, Emperor Gaozu Liu Bang enfeoffed several founding heroes, including Han Xin, Peng Yue, and Ying Bu, as kings across the realm. Unexpectedly, these heroes, relying on their military power, dominated their territories and even openly opposed the imperial court.
To secure his rule, Liu Bang systematically eliminated all non-royal kings and decreed that only members of the Liu family could hold the title. He then enfeoffed his sons, nephews, and brothers as feudal princes, believing that by making them "as interdependent as lips and teeth, as attached as bone and flesh," the Liu clan could firmly hold the empire.
But things did not go as planned. By the time of Emperor Jing of Han, these kings of the same surname had grown increasingly powerful and frequently stirred up rebellions. Finally, in 154 BCE, the Rebellion of the Seven Kingdoms erupted, led by Liu Pi, the King of Wu. Fortunately, Grand Commandant Zhou Yafu led an army to suppress the revolt, bringing the chaos to an end.
However, many other lords of the same surname still held vast territories, and the imperial court regarded them as a grave threat.
After Emperor Liu Che of the Han Dynasty ascended the throne, many ministers argued that the policy of reducing feudal princes' territories, proposed by Imperial Censor-in-Chief Chao Cuo during Emperor Jing's reign, was correct. They submitted memorials listing the princes' crimes and urged the new emperor to take action.
The feudal princes, upon hearing this, declared, "We are all the flesh and blood of the late emperor. He divided the land among us, interlocking our territories like dog's teeth, so that we might support each other, defend the capital, and make the Liu family's rule as solid as a rock. Now someone falsely accuses us—how unjust this is!"
In 138 BC, Liu Sheng, Prince Jing of Zhongshan, and Liu Deng, Prince of Dai, came to the capital Chang'an for an audience. Emperor Wu of Han hosted a banquet in the inner hall. During the feast, Liu Sheng suddenly wept sorrowfully and said to the emperor, "Your Majesty, rumors are spreading everywhere. Please do not believe slanderous words that would drive a wedge between the bond of flesh and blood we brothers share."
Emperor Wu comforted them openly, but secretly issued the "Decree of Grace" to force the princes to divide their fiefs among their sons. This split large kingdoms into many small ones, weakening separatist regimes and greatly strengthening central authority.
Later, people used the idiom "interlocking like dog's teeth" to describe a border that is as jagged and uneven as a dog's teeth.
Source: *Book of Han*, "Biographies of the Thirteen Sons of Emperor Jing"
Meaning of the Idiom: Later, the Chinese idiom "犬牙交错" came to describe a border that is as jagged and uneven as a dog's teeth.