What does Zhang Qian mean by hollowing out?

Sima Qian said in Historical Records: Zhang Qian is connected with the western regions, "so the northwest is connected with Han. But Zhang Qian hollowed it out, and later let people in the past call it Bo Wanghou, thinking that quality (honesty) is related to foreign countries, and foreign countries believe it. " . Pei's Collection of Historical Records: "Yue: chisel, open, empty and clear. Open Xiyu Road. "

Hollow means opening the way.

Refers to Zhang Qian's opening of traffic between the Central Plains and the Western Regions.

Zhang Qian's hollowing out and Zhang Qian's mission to the Western Regions are synonymous.

In the first year of Jianyuan (BC 140), Liang Wudi wanted to attack the Huns jointly with Da Yue, and Zhang Qian was recruited as the envoy. In the second year of Jianyuan, he left Longxi and was captured by Xiongnu. After escaping, I went west to Dawan, passed Kangju, arrived at Dayue's house, and went to Daxia, where I stayed for more than a year before coming back. On his way home, Zhang Qian changed from South Road to Nanshan in an attempt to avoid being discovered by Xiongnu, but he got it from Xiongnu and was detained for more than a year. In the third year of Yuan Shuo (BC 126), the Huns were in civil strife, and Zhang Qian took the opportunity to escape into the Han Dynasty. He gave a detailed report on the Western Regions to Emperor Wu of Han Dynasty, who made him a doctor in Taichung. Because of Zhang Qian's prestige in the Western Regions, the envoys of the Han Dynasty later called him Bo Wanghou to win the trust of other countries. Zhang Qian has made outstanding contributions to the opening of the Silk Road from China to the Western Regions, which is praised by the world.