Cheng Yu
When Yuan Shao defeated Gongsun Zan and congregated the four provinces north of the Yellow River, he assembled an army of over 100,000 to declare war against Cao Cao. Cheng Yu was made a general and was stationed in Juancheng with 700 soldiers. Cao Cao then sent a letter to Cheng Yu and asserted to Cheng Yu that he would send 2,000 men as reinforcements. However, Cheng Yu replied: "Yuan Shao has 100,000 men and considers himself invincible. If he sees I only have such a small army, he will not attack easily. On the contrary, if my position is strong (enough to threaten his movement), then he will not be able to pass me by without attacking; if he attacks, he'll surely win, so it will be a mere waste to send in reinforcement. I hope you could understand my rationale and don't doubt on that." Cao Cao was happy that he did not need to send additional troops to Cheng Yu, and was able to defeat Liu Bei in Xu Province within a short time.