Shih's commentary, in the words of the T`IEN-I-KO catalogue,
"contains helpful additions" here and there, but is chiefly
remarkable for the copious extracts taken, in adapted form, from
the dynastic histories and other sources.

11. CHANG YU. The list closes with a commentator of no
great originality perhaps, but gifted with admirable powers of
lucid exposition. His commentator is based on that of Ts`ao
Kung, whose terse sentences he contrives to expand and develop in
masterly fashion. Without Chang Yu, it is safe to say that much
of Ts`ao Kung's commentary would have remained cloaked in its
pristine obscurity and therefore valueless. His work is not
mentioned in the Sung history, the T`UNG K`AO, or the YU HAI, but
it finds a niche in the T`UNG CHIH, which also names him as the
author of the "Lives of Famous Generals." [46]
It is rather remarkable that the last-named four should all
have flourished within so short a space of time. Ch`ao Kung-wu
accounts for it by saying: "During the early years of the Sung
dynasty the Empire enjoyed a long spell of peace, and men ceased
to practice the art of war. but when [Chao] Yuan-hao's rebellion
came [1038-42] and the frontier generals were defeated time after
time, the Court made strenuous inquiry for men skilled in war,
and military topics became the vogue amongst all the high
officials. Hence it is that the commentators of Sun Tzu in our
dynasty belong mainly to that period. [47]

Besides these eleven commentators, there are several others
whose work has not come down to us. The SUI SHU mentions four,
namely Wang Ling (often quoted by Tu Yu as Wang Tzu); Chang Tzu-
shang; Chia Hsu of Wei; [48] and Shen Yu of Wu. The T`ANG SHU