Zhang Qian’s Mission to the Western Regions, Opening the Silk Road
To ally with the Yuezhi against the Xiongnu, Emperor Wu of Han sent Zhang Qian as envoy to the Western Regions; Zhang Qian was twice detained by the Xiongnu for more than a decade on the way, and, after many hardships, at last completed his mission — though he failed to achieve the original aim of a military alliance, he brought back a wealth of first-hand geographical and political intelligence about the states of Central Asia, accidentally opening the East–West trade route later called the "Silk Road," a feat Sima Qian called "the piercing through."