The Hidden Nature of Power (Hu Qian Jing, 虎鈐經)is one of the most important military works in Chinese history. It is regarded as an extraordinary book, as it takes the principle of Three Phenomena (Heaven, Earth and Mankind, i.e. "三才") into the calculation and utilization of all factors in war; and uses the regulation of Yin(陰) and Yang(陽) to elaborate the original and changing factors involved in warfare. This "extraordinary" nature has had a somewhat limited accessibility to a large part of the society of research for a long time, and is now available for the first time with the dedicated translation and research of author Adam E. Kryder.