18. All warfare is based on deception.
The truth of the pithy and profound saying will be admitted by every soldier. Col. Henderson tells us that Wellington, great in so many military qualities, was especially distinguished be “the extraordinary skill with which he concealed his movements and deceived both friend and foe.”
19. Hence, when able to attack, we must seem unable; when using our forces, we must seem inactive; when we are near, we must make the enemy believe we are far away; when far away, we must make him believe we are near.
20. Hold out baits to entice the enemy. Feign disorder, and crush him.
取, as often in Sun Tzǔ, is used in the sense of 擊. It is rather remarkable that all the commentators, with the exception of Chang Yü, refer 亂 to the enemy: “when he is in disorder, crush him.” It is more natural to suppose that Sun Tzŭ is still illustrating the uses of deception in war.
21. If he is secure at all points, be prepared for him. If he is in superior strength, evade him.
The meaning of 實 is made clear from chap. VI, where it is opposed to 虛 “weak or vulnerable spots.” 强, according to Tu Yu and other commentators, has reference to the keenness of the men as well as to numerical superiority. Capt. Calthrop evolves an extraordinarily far-fetched translation: “If there are defects, give an appearance of perfection, and avoid the enemy. Pretend to be strong, and so cause the enemy to avoid you”!
22. If your opponent is of choleric temper, seek to irritate him. Pretend to be weak, that he may grow arrogant.
I follow Chang Yü in my interpretation of 怒. 卑 is expended by Mei Yao-ch‘ên into 示以卑弱. Wang Tzŭ, quoted by Tu Yu,