軍爭篇 NO.5：

三軍可奪氣，將軍可奪心。
是故朝氣銳，晝氣惰，暮氣歸。
善用兵者，避其銳氣，擊其惰歸，此治氣者也。
以治待亂，以靜待嘩，此治心者也。
以近待遠，以佚待勞，以飽待饑，此治力者也。
無邀正正之旗，無擊堂堂之陣，此治變者也。

這句啥意思：

對于敵方三軍，可以挫傷其銳氣，可使喪失其士氣，對于敵方的將帥，可以動搖他的決心，可使其喪失斗志。
所以，敵人早朝初至，其氣必盛；陳兵至中午，則人力困倦而氣亦怠惰；待至日暮，人心思歸，其氣益衰。
善于用兵的人，敵之氣銳則避之，趁其士氣衰竭時才發起猛攻。這就是正確運用士氣的原則。
用治理嚴整的我軍來對付軍政混亂的敵軍，用我鎮定平穩的軍心來對付軍心躁動的敵人。這是掌握并運用軍心的方法。
以我就近進入戰場而待長途奔襲之敵；以我從容穩定對倉促疲勞之敵；以我飽食之師對饑餓之敵。這是懂得并利用治己之力以困敵人之力。
不要去迎擊旗幟整齊、部伍統一的軍隊，不要去攻擊陣容整肅、士氣飽滿的軍隊，這是懂得戰場上的隨機應變。

英文這么說：

A whole army may be robbed of its spirit;a commander-in-chief may be robbed of his presence of mind.
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.
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.
Disciplined and calm, to await the appearance of disorder and hubbub amongst the enemy:--this is the art of retaining self-possession.
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.
To refrain from intercepting an enemy whose banners are in perfect order, to refrain from attacking an army drawn up in calm and confident array:--this is the art of studying circumstances.

成語故事

公元前684年，齊國恃強凌弱攻打魯國，魯莊公率軍在長勺迎敵，兩軍相遇，齊軍擂起戰鼓，魯軍在曹劌的帶領下為避其銳氣沒有擂鼓。齊軍第三次擂鼓時士氣已經低落，魯軍才第一次擂鼓。魯軍靠的就是一鼓作氣的士氣以少勝多打敗齊軍。--《避其銳氣，擊其惰歸》