Hanzi

During the Warring States period, Prince Dan of Yan was held hostage in Zhao, where he befriended Ying Zheng, who had not yet become the King of Qin.

Later, Ying Zheng returned to Qin and became its king. Prince Dan was also held hostage in Qin, but Ying Zheng did not show any old affection or special treatment; instead, he treated him coldly and made things difficult for him. Seeing this, Prince Dan found an opportunity to escape back to Yan.

After returning, Prince Dan harbored a strong desire for revenge against Ying Zheng. However, his state was small and weak, making it difficult to realize his wish. Soon after, Qin dispatched troops to attack Qi, Chu, Han, Wei, and Zhao, gradually approaching Yan. The King of Yan was terrified, and Prince Dan was deeply worried.

He sought advice from his teacher, Ju Wu, on how to resist Qin's invasion. Ju Wu said, "I have a good friend named Tian Guang. He is very resourceful and cunning. You can discuss it with him."

Tian Guang was invited, and Prince Dan treated him with great respect, saying, "I hope you can help us find a way to resist Qin's invasion." Tian Guang listened, said nothing, and then took Prince Dan's hand and walked outside. He pointed to a horse tied to a large tree and said, "This is a fine breed of horse. In its prime, it can run more than a thousand li in a day. But when it grows old, even an inferior horse can run ahead of it. Why do you think that is?" Prince Dan replied, "That's because its strength has declined."

"Exactly!" Tian Guang continued, "What you've heard about me is from my prime years. You don't know that I am old now, and my energy is failing." Tian Guang paused and then added, "Of course, while I am powerless regarding important national affairs, I would like to recommend someone to you—my good friend Jing Ke. He is capable of undertaking this great responsibility."

Later, Prince Dan befriended Jing Ke and sent him to assassinate the King of Qin, but the assassination ultimately failed.