In 1405, a fleet of 317 wooden ships carrying nearly 28,000 men set sail from China, a floating city and the largest maritime force the world had ever seen. At its command was a man who began life as a captured, castrated slave, and whose existence China's own historians later tried to erase.

This episode opens the sources on Admiral Zheng He, whose treasure fleets reshaped Indian Ocean trade a full century before Columbus. We follow his rise from a war-orphaned boy in Yunnan to the right hand of an emperor, the secret motives behind the voyages, and the dramatic political reversal that grounded the fleets forever.

• The paradoxical eunuch system that made stripped, isolated captives the emperor's most trusted instruments of power
• Zheng He's brutal origin: captured at 10, castrated, and his defense of a reservoir during the ...