The encyclopedia · Strategy & Leadership · Strategic decision · 655 BCE
The Duke of Yu lent his neighbour a road — and lost his state on the way back
Jin asked to pass through Yu to attack Guo. The advisor said: when the lips are gone, the teeth are cold. The Duke said: they are family.
State of Yu · State of Jin
From historyHistory and classical literature, legend included. An analogy to think with, not a modern precedent.
What it means today
When a stronger partner asks for access that removes your buffer — a distribution deal, a shared platform, a data integration — kinship is not safety. The question is what happens when they come back.
What happened
In 655 BCE, the Marquis of Jin sent envoys to the small state of Yu asking permission to march troops through its territory to attack the neighbouring state of Guo. Jin offered jade and horses as gifts. The Duke of Yu accepted and agreed.
His senior advisor Gong Zhiqi remonstrated: 'Guo is the outer screen of Yu. If Guo perishes, Yu will certainly follow. The proverb says: the cheek and the jaw support each other; when the lips are gone, the teeth are cold. This refers to Yu and Guo.' He argued that Jin's kinship claims meant nothing — Jin had already destroyed its own closer relatives, the Huan and Zhuang branches, simply because they were threatening.
The Duke of Yu dismissed the warning twice. First he said: 'Jin is of our own clan. How could it harm us?' Then, when Gong Zhiqi pressed further, he said: 'My sacrificial offerings are abundant and pure. The spirits will surely support me.' Gong Zhiqi replied that spirits follow virtue, not ritual, and that if Jin took Yu and governed well, the spirits would accept Jin's offerings instead.
The Duke did not listen. Gong Zhiqi left with his entire clan, predicting: 'Yu will not reach the year-end sacrifice. On this campaign, Jin will not have to raise troops again.' In the twelfth month, Jin destroyed Guo. On the return march, the Jin army lodged at Yu, attacked, and destroyed it. The Duke of Yu was captured.
Why it happened
- The Duke of Yu confused kinship for safety: Jin shared his ancestral name, so he assumed shared interest — but Jin had already killed closer kin when they became inconvenient
- The immediate gift (jade and horses) made the long-term cost invisible: the road was free to lend, and the consequence was months away and belonged to someone else first
- The Duke's second defence — divine protection through correct ritual — substituted a feeling of safety for an analysis of the threat, ending the conversation where it needed to continue
- Gong Zhiqi's analysis was complete and correct, but he had no mechanism to compel the decision: the advice was given, refused, and the advisor's only remaining move was to leave
The lesson
A buffer that belongs to someone else is still your buffer. The Duke did not attack Guo — he merely let someone pass through. The cost was invisible until the army came back.
Aftermath
Gong Zhiqi's prediction proved exact: Jin destroyed both states in a single campaign. The phrase 唇亡齒寒 (when the lips are gone, the teeth are cold) entered the Chinese language as the standard warning against sacrificing a partner's defence for a short-term accommodation.
Sources
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