The Book of Army Management says:
It is perhaps significant that none of the earlier commentators
give us any information about this work. Mei Yao-ch‘ên calls it
軍之舊典 “an ancient military classic,” and Wang Hsi, 古軍書 “an old
book on war.” Considering the enormous amount of fighting that had
gone on for centuries before Sun Tzŭ’s time between the various
kingdoms and principalities of China, it is not in itself
improbable that a collection of military maxims should have been
made and written down at some earlier period.
On the field of battle,
Implied, though not actually in the Chinese.
the spoken word does not carry far enough: hence the institution of
gongs and drums.
I have retained the words 金鼓 of the original text, which recur in
the next paragraph, in preference to the other reading 鼓鐸 “drums
and bells,” which is found in the _T‘ung Tien_, _Pei T‘ang Shu
Ch‘ao_ and _Yü Lan_. 鐸 is a bell with a clapper. See _Lun Yü_ III.
24, _Chou Li_ XXIX. 15, 29. 金 of course would include both gongs
and bells of every kind. The _T‘u Shu_ inserts a 之 after each 爲.
Nor can ordinary objects be seen clearly enough: hence the institution
of banners and flags.