Gong Zhiqi said 'lips gone, teeth cold.' The Duke of Yu ignored him — and lost his kingdom

In 658 BCE, Duke Xian of Jin sent his minister Xun Xi to the neighbouring state of Yu with a bribe — four thoroughbred horses from Quchan and a jade disc from Chuiji — and asked to borrow a road through Yu to attack the state of Guo. Gong Zhiqi, a senior counsellor of Yu, warned the Duke that Jin's real target was not Guo alone. The Duke of Yu, dazzled by the gifts, granted passage. Jin's army, reinforced by Yu's own troops, captured the fortress of Xiayang from Guo.

Three years later, in 655 BCE, Jin asked again. Gong Zhiqi delivered what became the most famous warning in Chinese strategic literature: 'Guo is Yu's outer wall. When Guo falls, Yu will follow. The common saying — lips gone, teeth cold — describes exactly what Yu and Guo are to each other.' He argued that Jin had already destroyed the cadet branches of its own ruling house and would not spare a neighbour. The Duke of Yu replied that Jin was of the same ancestral clan and that the gods would protect him because his sacrifices were generous.

Gong Zhiqi countered that the gods favour virtue, not ritual, and that a Jin that had just destroyed one state would not hesitate to destroy another. The Duke ignored him and authorised the passage. Gong Zhiqi gathered his clan and fled Yu, saying: 'Yu will not last until the winter sacrifice. Jin will not need another campaign.'

In the winter of 655 BCE, Jin destroyed Guo. The army returned, encamped at Yu, and in a surprise attack extinguished Yu itself. The Duke of Yu was captured and taken to Jin as a prisoner. The fine horses and the jade disc, which the Duke of Yu had treasured, returned to Jin — Xun Xi presented them to Duke Xian with the remark: 'The horses are the same age; only their teeth have grown.'