Seeking an alliance with the Yuezhi
Zhang Qian came from Hanzhong and served as an attendant during Emperor Wu's Jianyuan period. The Han court learned that the Yuezhi had moved west after attacks by the Xiongnu and sought an ally against that power. Zhang Qian volunteered for the mission. He traveled with Tangyi Fu and others, but was detained after leaving Longxi and entering Xiongnu-controlled territory.
His biography describes years in captivity, marriage and a child, followed by escape and further travel through Dayuan and Kangju to the Great Yuezhi. The Yuezhi had established themselves near Daxia and were not willing to undertake the proposed campaign. Zhang Qian was detained again on the return journey before escaping with his wife and Tangyi Fu. The intended alliance failed, but the journey produced substantial knowledge of Central Asian places and political relationships.
Reports built from travel and inquiry
The Shiji distinguishes places Zhang Qian had visited from neighboring countries known through reports. His account concerned settlements, farming, money, trade and military organization. Information about more distant regions came partly from conversations along the way. The resulting geographical knowledge combined observation with inquiry rather than making him an eyewitness to every place described.
In Daxia he saw bamboo products from Qiong and cloth from Shu. Local traders said they obtained such goods through Shendu, leading him to propose a southwestern approach from Han territory. Attempts to investigate that route encountered resistance and did not achieve the passage he envisaged. The episode records existing commercial circulation as well as the conversion of a traveler's inference into an unsuccessful policy experiment.
The Wusun mission and continuing diplomacy
Zhang Qian subsequently joined campaigns against the Xiongnu. Knowledge of routes, water and grazing contributed to his promotion as Marquis of Bowang, although a later military failure cost him the title. Emperor Wu then adopted another diplomatic proposal and sent him with a larger mission to Wusun, carrying animals, valuables and subordinate envoys. Internal divisions limited the Wusun ruler's ability to accept the proposed relocation and alliance.
Zhang Qian dispatched deputies to several neighboring states, while Wusun representatives accompanied him back to Han. He became a senior official responsible for diplomatic reception and died soon afterward, but the dispatched envoys and later missions continued their work. His historical significance grew through these connected journeys, reports and decisions by many participants, rather than through the instantaneous founding of one road or an uninterrupted corridor.