A Thirteen-Year Mission
Zhang Qian, sent as envoy to the Yuezhi, was captured and held by the Xiongnu for more than a decade on the way, the Xiongnu chief even marrying him to a Xiongnu woman to win him over, and he had children, but Zhang Qian all the while secretly kept the tally-token representing the Han, never forgetting his diplomatic mission, and at last found a chance to escape and, through countless hardships, reached the Yuezhi — this tenacious persistence over thirteen years thereafter became a symbol in Chinese history of the diplomatic spirit of "keeping faith with the token and never wavering in resolve."
The "Piercing Through" of the Western Regions
Though Zhang Qian failed to complete the original diplomatic mission of allying with the Yuezhi to pincer the Xiongnu, he brought back detailed geographical and political intelligence on the states of Central Asia never before grasped in the Central Plains, and Sima Qian praised this feat as "the piercing through" (meaning the opening of a channel wholly unknown before); the Han thereafter gradually established trade relations with the states of the Western Regions on this basis, and the East–West trade route later called the "Silk Road" was thereby formally opened, profoundly changing the pattern of trade and cultural exchange across Eurasia for the nearly two thousand years after.