After a final voyage in 1433, expeditions were halted and the fleet was retired and ultimately burned. Ending China’s navy was one of the major changes made by Yongle’s descendants. The burning of the Chinese fleet left a power vacuum in the South China Sea, which in the sixteenth century was filled by Japanese and Chinese coastal pirates. Finally, shortly after Yongle and Zheng He’s deaths, China was challenged from the north again. Sixteen years after Zheng He’s final expedition, Yongle’s great grandson, the sixth Ming emperor, was captured and held hostage by Mongol raiders in 1449.

Zheng He’s first expedition left China in July 1405 with 62 large ships, over 200 smaller ships, and 28,000 soldiers. The largest ships were 425 feet long, over six times the length of the 65-foot caravels the Spanish and Portuguese would use on their explorations nearly a century later. China’s four-decked, 1,500-ton flagships had shallow drafts to allow them to navigate in river estuaries and watertight bulkheads to protect them from sinking. Their nine masts were up to two hundred feet tall and fitted with rattan sails.

But when his first son, the crown prince, died, Hongwu  left his throne to the son of his favorite son, rather than picking one of his other sons.. Hongwu’s grandson became emperor at 20, but his reign was a short one. His uncle Zhu Di, the emperor’s younger son, had been passed over for the crown but remained prince of a northern territory around Dadu, the previous Yuan capital close to the Mongol border.

Administration of the empire by Confucian scholars was reinstated, along with the elaborate system of civil service examinations. Remembering the suffering and famines during his youth, partly caused by the flooding of the Yangtze River, Hongwu promoted public works and infrastructure projects including new dikes and irrigation systems to serve an agricultural system dominated by paddy rice. He organized the building or repair of nearly 41,000 reservoirs and planted over a billion trees in his land reclamation program.