This was the plan Chen Deng proposed to Liu Bei, "Yuan Shao is Cao Cao's terror. He is strongly posted in an extensive territory of four regions---Jizhou, Qingzhou, Youzhou, and Bingzhou---with one million fighting soldiers and numerous able officers. Write letters and pray him rescue you."

Liu Bei replied, "But we have never had any dealings with each other, and he is unlikely to do such a thing for a person who has just destroyed his brother."

"There is someone here whose family have been on intimate terms with the Yuans for a hundred years. Yuan Shao would surely come, if he wrote."

"And who is this?"

"A man you know well and respect greatly. Can you not guess?"

"You surely mean Zheng Xuan," said Liu Bei suddenly.

"That is he," said Chen Deng smiling.

Now Zheng Xuan was a student and a man of great talent, who had long studied under the famed teacher Ma Rong, whose knowledge of the Book of Odes was universally recognized.Whenever Ma Rong lectured, he let fall a curtain behind which were a circle of singing girls. The students were assembled in front of this curtain. Zheng Xuan attended these lectures for three years and never once let his eyes wander to the curtain.

Naturally the master admired his pupil. After Zheng Xuan had finished his studies and gone home, Ma Rong praised him to the others, saying, "Only one man has penetrated the inner meaning of my instructions, and that one is Zheng Xuan."

In Zheng Xuan's household, the waiting maids were familiar with the Book of Odes. Once one of the maids opposed Zheng Xuan's wishes, so as punishment she was made to kneel in front of the steps. Another girl made fun of her, quoting from an ode:

"What are you doing there in the mire?"

The kneeling girl capped the verse from another ode, quoted she:

"That was but a simple word I said, Yet brought it wrath upon my head."

Such was the family in which Zheng Xuan had been born. In the reign of the Emperor Huan, he rose to the rank of Chair of the Secretariat.But when the Ten Eunuchs began to control the government, he gave up office and retired into the country to Xuzhou.Liu Bei had known him before, had consulted him on many occasions, and greatly respected him.

Liu Bei was glad that he had remembered this man, and without loss of time, in company with Chen Deng, he went to Zheng Xuan's house to ask him to draft this letter, which Zheng Xuan generously consented to do.

Sun Qian was entrusted with the task of delivery and set out at once. Yuan Shao read it and considered the matter long before speaking.

"Liu Bei destroyed my brother, and I ought not to help him, but out of consideration for the writer of this letter I must."

Thereupon Yuan Shao assembled his officers to consider an attack upon Cao Cao.