Emperor Liu Che of the Han Dynasty was reluctant to humiliate the Xiongnu, and in order to defeat the meat slaves, he tried to unite all forces against the Xiongnu. Hearing that the skull of the king of the Great Moon Clan was cut off by the Xiongnu to make a wine vessel, the Great Moon Clan moved the country westward, and Emperor Wu of han decided to send Zhang Qian to the Western Regions to unite with the Great Moon Clan to attack the Xiongnu. The ancient Ōtsuki kingdom was about the area around present-day Afghanistan.
In 138 BC, the ambitious Zhang Qian was ordered by Emperor Wu of Han to set out with 100 warriors and supplies. Tang Yi's father served as a guide and translator, and he was a Hun who submitted to the Han Dynasty.
To go to the Great Moon Clan, you must pass through the territory of the Xiongnu, and before a few days, Zhang Qian and his party were discovered by the Xiongnu soldiers and seized and locked up, this pass is 10 years.
In the past 10 years, Zhang Qian has never forgotten his mission and always wants to escape. Finally, one day, Zhang Qian took advantage of the guards' lack of attention and escaped with his father and came to a country called Dawan (in present-day Uzbek Republic). The king was very aware of the strength and wealth of the Western Han Dynasty and entertained the envoys of the Han Dynasty very warmly. He also sent someone to escort them to the Ōtsuki Clan Kingdom.
Unfortunately, after the Ōtsuki clan moved to the vicinity of Bactria (in present-day Northern Afghanistan), they did not want to fight any more, so they refused Zhang Qian's request, and Zhang Qian and his father lived there for more than a year, but failed to convince them, and had to return disappointed. At this time, it has been exactly 13 years since he left Chang'an.
Dunhuang mural Zhang Qian out of the western region
Although the goal was not achieved, this mission to Xicheng gave Zhang Qian a more detailed understanding of the situation in Xicheng, and reported to Emperor Wu of Han one by one: When we were in the Kingdom of Bactria (near present-day Stan balkh in Afghanistan), we saw fine cloth produced in Shudi, and the locals told us that they had bought it from the merchants of Tianzhu (the collective name of ancient China for present-day India and the countries of the Indian subcontinent). Since Tianzhu and Shudi were in trade, it meant that Tianzhu was not far from Shudi.
So Emperor Wu of Han sent Zhang Qian with a large number of gifts to set out from Shudi to find Tianzhu. As a result, he traveled thousands of miles, did not find Tianzhu, but accidentally befriended the State of Yunnan (present-day eastern Yunnan Province). Emperor Wu of Han felt very satisfied and rewarded Zhang Qian again.
After the Xiongnu were driven north of the desert by Wei Qing and Huo, many countries in the western region were freed from Xiongnu control. In 119 BC, Zhang Sai once again sent an envoy to the Western Regions with 300 warriors, as well as a large amount of gold, cattle and sheep and other gifts. He first went to the Wusun Kingdom (near the Tianshan region) to establish friendly relations with the Wusun Kingdom, and then sent his deputies to the countries of Dawan and Dayue.
Since then, the Han Dynasty has established close diplomatic relations with the Western Regions.