Plot

(The story of Zheng and Duan continues.)

A few months later, Zheng's mother urged Duan to build walls, stockpile arms and recruit mercenaries to the rebel cause. Soon news of all this reached the capital, and it was clear to everybody what was going to happen. Zheng's ministers urged him to retake the city from his brother before it was too late. However, Zheng dismissed these proposals, stating that he found no fault in Duan, and it could not be proved that he was plotting a coup. Besides, Duan was his brother, and he could not take up arms against him.

Soon Zheng had left the dukedom to Luoyang for some diplomatic matters; his mother (who was staying in the capital) wrote a letter to Duan, ordering him to revolt at that moment and she would open the gates of the capital for him. So Duan revolted against Duke Zheng, and not long after he was under the capital walls.

However, Zheng was well prepared, and it was all his trap. Duan's army melt away quickly, and he had nowhere to run. At last, Duan cut his throat. Zheng rushed to see his brother's corpse; weeping greatly, and he said to him, "My brother, you knew that I would always forgive you; why has it come to this?"

PS. Of course, in real life Zheng was nowhere near as compassionate - he only did it for show.

After all, if Zheng did not appear to be tolerant from the beginning, he would have no chance (or excuse) to eliminate his brother.