He goes on to remark that Tsʽao Tsʽao’s commentary on Sun Tzǔ leaves a certain proportion of difficulties unexplained. 41 This, in Tu Mu’s opinion, does not necessarily imply that he was unable to furnish a complete commentary. According to the Wei Chih , Tsʽao himself wrote a book on war in something over 100,000 words, known as the 新書 . It appears to have been of such exceptional merit that he suspects Tsʽao to have used for it the surplus material which he had found in Sun Tzǔ . He concludes, however, by saying: “The