Did one captured envoy really open the way west for the Han empire?

Not by himself, and not on purpose, but his reports helped. Zhang Qian was a Han military officer sent west as an envoy in 138 BC, and he was one of the first official diplomats to bring the Han court valuable information about Central Asia. His goal was military, not commercial: to find the Yuezhi and build an alliance against the Xiongnu, the nomads who controlled Inner Mongolia, dominated the Western Regions and blocked outside contact.

The trip went badly. The Xiongnu captured him and held him for thirteen years. In that time he married, had a son and earned the trust of the Xiongnu leader, then escaped and carried on west. The Yuezhi, when he reached them, were too settled to want a war. Of the just over a hundred men who set out, only Zhang and his guide Ganfu managed to return.

Yet he came home in 125 BC with something valuable: detailed news that sophisticated civilizations existed to the West, with which China could advantageously develop relations. He had also noticed the tall, powerful Ferghana horses, which the Han wanted so much that they later fought two campaigns to get them.

Zhang did not set up trade himself. But his efforts eventually led to a trade mission to the Wusun people in 119 BC, which led to trade between China and Persia. That is why he is revered in China as a national hero, and why some accounts date the beginning of the Silk Road network to his missions. Others stress that some routes are far older: jade travelled the southern stretches as long ago as 5000 BCE.