Su Li was a political and diplomatic strategist during the Warring States period. Once, he heard that General Bai Qi of Qin was about to lead troops to attack Daliang, the capital of Wei. If Daliang were captured by Qin, the nearby Western Zhou royal house would be in danger.

Therefore, Su Li said to King Zhou, "In recent years, Bai Qi has defeated states like Han and Zhao, seizing many territories. Now he is going to attack Daliang, and if Daliang falls to Bai Qi, the Zhou royal house will be in peril! You should find a way to stop Bai Qi from mobilizing his troops." So, King Zhou sent Su Li to Qin.

Su Li said to Bai Qi, "Once upon a time, there was a man named Yang Youji from the state of Chu, who was an expert archer. He would shoot arrows at a willow leaf from a hundred paces away, hitting the center of the leaf with every single arrow—a hundred shots, a hundred hits. Everyone watching praised his skill, but a passerby remarked, 'This man could be taught how to shoot.' Yang Youji was displeased when he heard this and said, 'Everyone says I shoot well, yet you say I could be taught. Why don't you try shooting that willow leaf yourself?' The passerby replied, 'I cannot teach you the technique of extending your left arm and bending your right arm for archery. However, have you considered that although you hit the willow leaf a hundred times out of a hundred, you are not good at resting? If you get tired and miss just one shot, all your previous efforts will be in vain.'"

After telling this story, Su Li brought the conversation back to Bai Qi, saying, "You have already defeated states like Han and Zhao and acquired many territories, achieving great merit. Now, you are ordered to lead troops out of the pass, passing through the Western Zhou royal domain to attack Daliang. If this battle is not victorious, all your previous achievements will be nullified. It would be better for you to claim illness and not go on this expedition."

Bai Qi listened and laughed, saying, "I am invincible and win every battle; how could I not achieve victory?" Thus, he was not swayed by Su Li. He led his troops to attack Wei and indeed won another great victory, seizing dozens of cities from Wei.