Yong-le: Year 4, Month 7, Day 13
27 Jul 1406
Instructions were issued to the Cheng-guo Duke Zhu Neng, regional commander for the expedition being sent to punish Annam. The instructions read: "It has been heard that, although the weather in Annam is hot, after midnight it becomes very cool. If one lacks covering, it is very easy to fall ill. The winter months are also cold and fires are necessary. The army should prepare wadded clothing. Also the man are skilled in poisoning. The soldiers should sink wells for drinking water and slaughter their own food."
Zhong-yang Yan-jiu yuan Ming Shi-lu, volume 11, page 829