Each feudal dynasty had loyal courtiers, and the Han Dynasty had such a courtier, who sent envoys to the Xiongnu but was detained by the Xiongnu. Shan Yu of the Xiongnu admired his talent, so Shan Yu's many retentions failed to change his loyalty, and this courtier was Su Wu. In later novels, many novels changed Su Wu to the image of a military general, but in fact, Su Wu was a civilian. Su Wu's father was also an official of the Han Dynasty, so Su Wu was enlisted as an official by Enyin, and when Su Wu became an official, the emperor of the Han Dynasty was Emperor Wu of Han.
Han Gaozu once went out to fight against the Xiongnu in the early Han Dynasty, but because the good generals of the Han Dynasty at that time were all old one after another, Han Gaozu personally went out on the expedition at that time and was defeated by the Xiongnu. Han Gaozu had no choice but to use gold, silver, treasure and beautiful women as tributes to close relations with the Xiongnu, and shan Yucai of the Xiongnu did not send troops to invade the Han Dynasty. The han dynasty's submission to the Xiongnu remained until the time of Emperor Wu of Han, who always wanted to change this foreign policy. Because of years of peace, the Han Dynasty accumulated a lot of financial resources, and the Han Dynasty already had good generals who could resist the Xiongnu. The Huns had not fought for many years, so they had developed a lazy character, and the army began to slacken off.
Emperor Wudi of the Han Dynasty saw the opportunity and took the initiative to sever the relationship between the Xiongnu and stopped offerings to the Xiongnu, so the Xiongnu sent troops to attack the Han Dynasty in one breath, but what they did not expect was that the generals and troops of the Han Dynasty were not vegetarians. Soon the Han Dynasty defeated the invading Xiongnu army, and the Han army also changed its usual defensive state, and after repelling the Xiongnu army, they also invaded the Land of the Huns. After the Xiongnu were defeated many times, they could only compromise with the Han Dynasty, and emperor Wudi of the Han Dynasty also consumed many years of accumulated treasury due to years of conquest, and the Han Dynasty needed to breathe, so the Han Dynasty and the Xiongnu reached a reconciliation, but the Han Dynasty changed its diplomatic policy.
In his later years, Emperor Wu of Han began to make overtures with the Xiongnu, and the Xiongnu sent envoys to the Han Dynasty to pay homage to Emperor Wu of Han, because of the principle of etiquette and exchange, so Emperor Wu of Han also sent envoys to the Xiongnu to show their sincerity. One of the envoys sent by Emperor Wu of Han included Su Wu, who had the new Shan Yu ascended the throne, so Su Wu was sent to congratulate him, but when Su Wu's visit was over and he was going to return to China, the Xiongnu government underwent a coup. The Xiongnu detained Su Wu, and although the Han Dynasty made many representations, the Xiongnu did not return Su Wu, so the relationship between the Han Dynasty and the Xiongnu was once at odds.
Shan Yu of the Xiongnu knew that Su Wu was a very talented man, so he retained Su Wu many times and offered attractive conditions such as money and official positions, but Su Wu resolutely refused. In a fit of rage, Shan Yu ordered his men to imprison him in the cellar, and Su Wu was coerced by such a harsh environment, but he still did not submit to the Xiongnu. After living without water and food for a few days, Shan Yu still released him, but Shan Yu proposed to release him back to the Han Dynasty as long as the rams of the North Sea gave birth to lambs. Since then, Su Wu has been escorted to the North Sea to herd sheep, and Su Wu has stayed for nineteen years.
After the death of Emperor Wu of Han, the relationship between Emperor Han Zhao and the Xiongnu was once again relaxed, so Emperor Han Zhao once again sent envoys to ask for Su Wu, but the Xiongnu always insisted that Su Wu was dead. Later, after many investigations, the envoys learned that Su Wu was imprisoned in Beihai shepherding sheep, so he once again proposed that Su Wu be su. The Xiongnu Shan Yu knew that the paper wrapper could not hold the fire, so he released Su Wu. After nineteen years of baptism, Su Wu has changed from a teenager to a white-haired old man, and after returning to the Han Dynasty, Emperor Han Zhao, in order to recognize Su Wu's loyalty, added him to the rank of knight. However, Su Wu was later dismissed from his official post by Huo Guang because of his son's involvement in a rebellion, and later Su Wu was given the title of Marquis of Guannei because he supported Emperor Xuan of Han.