The Book of Army Management says: On the field of battle, the spoken word does not carry far enough: hence the institution of gongs and drums. Nor can ordinary objects be seen clearly enough: hence the institution of banners and flags.
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 may be focused on one particular point.
民既专一，则勇者不得独进，怯者不得独退，此用众之法也。
The host thus forming a single united body, is it impossible either for the brave to advance alone, or for the cowardly to retreat alone. This is the art of handling large masses of men.
故夜战多金鼓，昼战多旌旗，所以变人之耳目也。
In night-fighting, then, make much use of signal-fires and drums, and in fighting by day, of flags and banners, as a means of influencing the ears and eyes of your army.
三军可夺气，将军可夺心。
A whole army may be robbed of its spirit; a commander-in-chief may be robbed of his presence of mind.
是故朝气锐，昼气惰，暮气归。
Now a soldier＇s spirit is keenest in the morning; by noonday it has begun to flag; and in the evening, his mind is bent only on returning to camp.
善用兵者，避其锐气，击其惰归，此治气者也。
A clever general, therefore, avoids an army when its spirit is keen, but attacks it when it is sluggish and inclined to return. This is the art of studying moods.
以治待乱，以静待哗，此治心者也。
Disciplined and calm, to await the appearance of disorder and hubbub amongst the enemy:--this is the art of retaining self-possession.
以近待远，以佚待劳，以饱待饥，此治力者也。
To be near the goal while the enemy is still far from it, to wait at ease while the enemy is toiling and struggling, to be well-fed while the enemy is famished:--this is the art of husbanding one＇s strength.
无邀正正之旗，无击堂堂之陈，此治变者也。