兵势
Combine the orthodox and the surprising — they endlessly generate each other, and victory comes from the surprising. Build momentum like dammed water, and release it at the decisive instant.
- What this chapter says
- Key lines
- Applied today
- Related stratagems
- Chapters that share ground with this one
What this chapter says
Having covered disposition (form), Sun Tzu turns to 势 — energy, force, momentum. Battle is joined with the orthodox, direct force (正) but decided by the unorthodox, surprising move (奇); and the two are inexhaustible, each giving rise to the other in an endless cycle, like a circle with no beginning or end. The skilled commander builds up potential energy and releases it at exactly the right moment — the rush of pent-up water that rolls boulders, the drawn crossbow loosed in an instant. Crucially, he 'looks to the effect of combined energy, and does not require too much from individuals': victory is sought from the momentum of the whole situation, not squeezed out of heroic individuals. Position ordinary people within an irresistible force and they achieve extraordinary things.
Key lines
From 十一家注孫子, the Eleven Commentators edition. The Chinese is verbatim from that text; the English beneath each is ours.
- 曹操 正者當敵，奇兵從傍擊不備也。 The regular force meets them head-on; the irregular strikes from the flank, where they are unready.
- 李筌 戰無其詐，難以勝敵。 War without its deceptions can hardly beat an enemy.
- 杜佑 正者當敵，奇者從傍擊不備。以正道合戰，以奇變取勝也。 The regular meets the enemy; the irregular strikes from the flank where he is unready. Join battle by the regular way, take the victory by irregular change.
- 梅堯臣 用正合戰，用奇勝敵。 Join battle with the regular; win with the irregular.
- 何氏 如戰國廉頗爲趙將，秦使間曰：「秦獨畏趙括耳，廉頗易與，且降矣。」會頗軍多亡失，數敗，堅壁不戰。又聞秦反間之言，使括代頗。至，則出軍擊秦。秦軍佯敗而走，張二奇兵以刼之。趙軍逐勝，追造秦壁，壁堅拒不得入。而秦奇兵二萬五千絶趙軍後，又五千騎絶趙壁間。趙兵分爲二，糧道絶，括卒敗。又，隋突厥犯塞，煬帝令唐高祖與馬邑太守王仁恭率衆備邊。會虜宼馬邑，仁恭以衆寡不敵，有懼色。高祖曰：「今主上遐遠，孤城絶援，若不死戰，難以圖全。」於是親選精騎四千，出爲遊軍，居處飲食，隨逐水草，一同於突厥。見虜候騎，但馳騁獵耳，若輕之。及與虜相遇，則掎角置陳，選善射者爲別隊，持滿以待之。虜莫能測，不敢決戰。因縱奇兵擊走之，獲其特勒所乘駿馬，斬首千餘級。又，太宗選精銳千餘騎爲奇兵，皆黑衣玄甲，分爲左右隊，建大旗，令騎將秦叔寶、程䶧金等分統之。每臨宼，太宗躬被玄甲，先鋒率之，候機而進，所向摧殄，常以少擊衆，賊徒氣懾。又，五代漢高祖在晉陽，郭進往依之，漢祖壯其材。會北虜屠安陽城，因遣進攻拔之，戎人遁去，授坊州刺史。虜主道斃，高祖出奇兵井陘，進以間道先入洺北，因定河北。此皆以奇勝之迹也。 Illustrated with Changping: Qin's agents spread word that only Zhao Kuo was feared, Zhao replaced the cautious Lian Po with him, and Qin then feigned flight while two irregular forces cut the Zhao army in two and severed its supply road. A second illustration follows from the Sui wars with the Turks.summary, not a translation
- 張預 兩軍相臨，先以正兵與之合戰，徐發奇兵或擣其旁、或擊其後以勝之，若鄭伯禦燕師，以三軍軍其前，以潛軍軍其後是也。 The two armies face each other; first join battle with the regular force, then release the irregular by degrees — striking his flank, or his rear — and so beat him. As when the Earl of Zheng met the Yan army, posting three divisions to their front and a hidden force to their rear.
- 孟氏 勢峻，則巨石雖重，不能止。 Where the fall is steep, even a great stone, heavy as it is, cannot hold.
- 杜佑 言水性柔弱，石性剛重，至於漂轉大石，投之洿下，皆由急疾之流，激得其勢。 Water is by nature soft and yielding, stone hard and heavy; that it should roll great stones and cast them into the hollows below is entirely because a rushing current has got its momentum.
- 張預 水性柔弱，險徑要路，激之疾流，則其勢可以轉巨石也。 Water is by nature soft and yielding; but funnel it through a narrow defile into a rushing current and its force can roll great stones.
- 杜佑 言勝負之道，自圖於中，不求之下，責怒師衆，彊使力進也，若秦穆悔過，不替孟明也。 It means the way of victory and defeat is settled within one's own counsel, not sought below by railing at the host and driving men forward by force — as Duke Mu of Qin repented and did not replace Mengming.
Applied today
Pair a solid, expected core with one unexpected move — the surprise is what wins. And time the release of built-up momentum (a launch, a campaign, a market entry) rather than relying on any single person's heroics.
Engineer favorable momentum so ordinary people produce extraordinary results — design the system's force and put good people in it, rather than expecting heroics to compensate for a situation stacked against them.