This chapter focuses on the two-decade reign of the third Ming emperor, the bellicose and ambitious usurper Yongle. The Yongle emperor had grown up in a martial world. Historians have shown that the Yongle period saw the highest sustained gun production levels of the entire early Ming period. The prince was saved by the arrival of some “barbarian cavalry troops,” most likely Mongols who had joined the Ming. China’s powerful guns had helped the Ming to create the world’s most powerful empire, unparalleled in military power, but it seems that the death of Yongle in 1424 also corresponded with the end of the period of rapid experimentation with guns and their administration. A set of regulations for firearm production and design that Yongle’s administration issued in 1414 formed the basic blueprint for Ming firearms production for the next century, “becoming the Ming Military production method for guns".