Duke Xiang of Jin once again borrowed the road of Yu State to attack Guo State. Gong Jian said, "Guo is the barrier of Yuzhou. When the State of Guo perishes, so does the State of Yu. The ambition of gold cannot be encouraged, and foreign enemies cannot be ignored. Lending the road to the state of Jin once is too much. How can there be a second time? As the saying goes,' cheek and gum bone are interdependent, and teeth will be frozen without lips.' This is the relationship between Yu and Guo. "