Ma Su was highly gifted and loved to discuss military plans, and Zhuge Liang thought very highly of him. On his deathbed, Liu Bei warned Zhuge Liang: “Ma Su’s words exceed his substance. He cannot be given great tasks. Watch him.” Zhuge Liang did not agree and often talked with Ma Su from morning until night.
In 228, many urged that veteran generals such as Wei Yan lead the vanguard. Zhuge Liang gave it to Ma Su instead. At Jieting, the Wei general Zhang He routed him. Ma Su died in prison, and Zhuge Liang wept for him. (Records of the Three Kingdoms)
The phrase yan guo qi shi, words beyond substance, comes from Liu Bei’s warning. Dictionaries define its original sense as boastful words that exceed real ability.