This photo reflects the story of Su wu, who was detained by the Xiongnu during the reign of Emperor Wu of Han, and was forced to herd sheep in the North Sea. He held the Han knot to herd sheep and remained unyielding.

During the reign of Emperor Wu of Han, the Han Dynasty continuously attacked the Xiongnu, and both sides continuously sent envoys to investigate each other.

In the first year of the Tianhan era (100 BC), Su Wu was ordered to serve as a general of Zhonglang to the Xiongnu. At that time, assistant Minister Zhang Sheng was involved in the internal turmoil of the Xiongnu, and Su Wu was implicated and detained. The Xiongnu nobles repeatedly threatened and tempted him to surrender. Su Wu swore to death not to obey, and stabbed himself with a sword. Later, he was moved by the Xiongnu people to the North Sea to herd sheep and threatened to have a son for the ram before he could be released and returned to China.

Su Wu went through hardships and stayed with the Xiongnu for nineteen years. He held the Han knot to herd sheep and remained unyielding. In the sixth year of the Shiyuan reign of Emperor Zhao of Han (81 BC), Han reconciled with the Xiongnu, and Han envoys found the whereabouts of Su Wu and others, which led to their release and return to Han.