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.
24. 夫金鼓旌旗者所以一民之耳目也
Gongs and drums, banners and flags, are means whereby the ears and eyes of the host
The original text, followed by the T‘u Shu, has 人 for 民 here and in the next two paragraphs. But, as we have seen, 人 is generally used in Sun Tzŭ for the enemy.
may be focussed on one particular point.
Note the use of 一 as a verb. Chang Yü says: 視聽均齊則雖百萬之衆進退如一矣 “If sight and hearing converge simultaneously on the same object, the evolutions of as many as a million soldiers will be like those of a single man”!
25. 民既專一則勇者不得獨進怯者不得獨退此用衆之法也
The host thus forming a single united body, it is impossible either for the brave to advance alone, or for the cowardly to retreat alone.