[Only about a third of the chapter, comprising ss. ss. 1-13, deals with "terrain," the subject being more fully treated in ch. XI. The "six calamities" are discussed in SS. 14-20, and the rest of the chapter is again a mere string of desultory remarks, though not less interesting, perhaps, on that account.]
1. Sun Tzu said: We may distinguish six kinds of terrain, to wit: (1) Accessible ground;
[Mei Yao-ch`en says: "plentifully provided with roads and means of communications."]
(2) entangling ground;
[The same commentator says: "Net-like country, venturing into which you become entangled."]
(3) temporizing ground;
[Ground which allows you to "stave off" or "delay."]
(4) narrow passes; (5) precipitous heights; (6) positions at a great distance from the enemy.
[It is hardly necessary to point out the faultiness of this classification. A strange lack of logical perception is shown in the Chinaman's unquestioning acceptance of glaring cross- divisions such as the above.]
2. Ground which can be freely traversed by both sides is called ACCESSIBLE.
3. With regard to ground of this nature, be before the enemy in occupying the raised and sunny spots, and carefully guard your line of supplies.
[The general meaning of the last phrase is doubtlessly, as Tu Yu says, "not to allow the enemy to cut your communications." In view of Napoleon's dictum, "the secret of war lies in the communications,"  we could wish that Sun Tzu had done more than skirt the edge of this important subject here and in I. ss. 10, VII. ss. 11. Col. Henderson says: "The line of supply may be said to be as vital to the existence of an army as the heart to the life of a human being. Just as the duelist who finds his adversary's point menacing him with certain death, and his own guard astray, is compelled to conform to his adversary's movements, and to content himself with warding off his thrusts, so the commander whose communications are suddenly threatened finds himself in a false position, and he will be fortunate if he has not to change all his plans, to split up his force into more or less isolated detachments, and to fight with inferior numbers on ground which he has not had time to prepare, and where defeat will not be an ordinary failure, but will entail the ruin or surrender of his whole army." 
Then you will be able to fight with advantage.
4. Ground which can be abandoned but is hard to re-occupy is called ENTANGLING.
5. From a position of this sort, if the enemy is unprepared, you may sally forth and defeat him. But if the enemy is prepared for your coming, and you fail to defeat him, then, return being impossible, disaster will ensue.
6. When the position is such that neither side will gain by making the first move, it is called TEMPORIZING ground.
[Tu Mu says: "Each side finds it inconvenient to move, and the situation remains at a deadlock."]
7. In a position of this sort, even though the enemy should offer us an attractive bait,
[Tu Yu says, "turning their backs on us and pretending to flee." But this is only one of the lures which might induce us to quit our position.]
it will be advisable not to stir forth, but rather to retreat, thus enticing the enemy in his turn; then, when part of his army has come out, we may deliver our attack with advantage.
8. With regard to NARROW PASSES, if you can occupy them first, let them be strongly garrisoned and await the advent of the enemy.
[Because then, as Tu Yu observes, "the initiative will lie with us, and by making sudden and unexpected attacks we shall have the enemy at our mercy."]
9. Should the army forestall you in occupying a pass, do not go after him if the pass is fully garrisoned, but only if it is weakly garrisoned.
10. With regard to PRECIPITOUS HEIGHTS, if you are beforehand with your adversary, you should occupy the raised and sunny spots, and there wait for him to come up.
[Ts`ao Kung says: "The particular advantage of securing heights and defiles is that your actions cannot then be dictated by the enemy." [For the enunciation of the grand principle alluded to, see VI. ss. 2]. Chang Yu tells the following anecdote of P`ei Hsing-chien (A.D. 619-682), who was sent on a punitive expedition against the Turkic tribes. "At night he pitched his camp as usual, and it had already been completely fortified by wall and ditch, when suddenly he gave orders that the army should shift its quarters to a hill near by. This was highly displeasing to his officers, who protested loudly against the extra fatigue which it would entail on the men. P`ei Hsing- chien, however, paid no heed to their remonstrances and had the camp moved as quickly as possible. The same night, a terrific storm came on, which flooded their former place of encampment to the depth of over twelve feet. The recalcitrant officers were amazed at the sight, and owned that they had been in the wrong. 'How did you know what was going to happen?' they asked. P`ei Hsing-chien replied: 'From this time forward be content to obey orders without asking unnecessary questions.' From this it may be seen," Chang Yu continues, "that high and sunny places are advantageous not only for fighting, but also because they are immune from disastrous floods."]
11. If the enemy has occupied them before you, do not follow him, but retreat and try to entice him away.
[The turning point of Li Shih-min's campaign in 621 A.D. against the two rebels, Tou Chien-te, King of Hsia, and Wang Shih-ch`ung, Prince of Cheng, was his seizure of the heights of Wu-lao, in spike of which Tou Chien-te persisted in his attempt to relieve his ally in Lo-yang, was defeated and taken prisoner. See CHIU T`ANG, ch. 2, fol. 5 verso, and also ch. 54.]
12. If you are situated at a great distance from the enemy, and the strength of the two armies is equal, it is not easy to provoke a battle,
[The point is that we must not think of undertaking a long and wearisome march, at the end of which, as Tu Yu says, "we should be exhausted and our adversary fresh and keen."]
and fighting will be to your disadvantage.
13. These six are the principles connected with Earth.
[Or perhaps, "the principles relating to ground." See, however, I. ss. 8.]
The general who has attained a responsible post must be careful to study them.
14. Now an army is exposed to six several calamities, not arising from natural causes, but from faults for which the general is responsible. These are: (1) Flight; (2) insubordination; (3) collapse; (4) ruin; (5) disorganization; (6) rout.
15. Other conditions being equal, if one force is hurled against another ten times its size, the result will be the FLIGHT of the former.
16. When the common soldiers are too strong and their officers too weak, the result is INSUBORDINATION.
[Tu Mu cites the unhappy case of T`ien Pu [HSIN T`ANG SHU, ch. 148], who was sent to Wei in 821 A.D. with orders to lead an army against Wang T`ing-ts`ou. But the whole time he was in command, his soldiers treated him with the utmost contempt, and openly flouted his authority by riding about the camp on donkeys, several thousands at a time. T`ien Pu was powerless to put a stop to this conduct, and when, after some months had passed, he made an attempt to engage the enemy, his troops turned tail and dispersed in every direction. After that, the unfortunate man committed suicide by cutting his throat.]
When the officers are too strong and the common soldiers too weak, the result is COLLAPSE.
[Ts`ao Kung says: "The officers are energetic and want to press on, the common soldiers are feeble and suddenly collapse."]
17. When the higher officers are angry and insubordinate, and on meeting the enemy give battle on their own account from a feeling of resentment, before the commander-in-chief can tell whether or no he is in a position to fight, the result is RUIN.
[Wang Hsi`s note is: "This means, the general is angry without cause, and at the same time does not appreciate the ability of his subordinate officers; thus he arouses fierce resentment and brings an avalanche of ruin upon his head."]
18. When the general is weak and without authority; when his orders are not clear and distinct;
[Wei Liao Tzu (ch. 4) says: "If the commander gives his orders with decision, the soldiers will not wait to hear them twice; if his moves are made without vacillation, the soldiers will not be in two minds about doing their duty." General Baden- Powell says, italicizing the words: "The secret of getting successful work out of your trained men lies in one nutshell--in the clearness of the instructions they receive."  Cf. also Wu Tzu ch. 3: "the most fatal defect in a military leader is difference; the worst calamities that befall an army arise from hesitation."]
when there are no fixes duties assigned to officers and men,
[Tu Mu says: "Neither officers nor men have any regular routine."]
and the ranks are formed in a slovenly haphazard manner, the result is utter DISORGANIZATION.
19. When a general, unable to estimate the enemy's strength, allows an inferior force to engage a larger one, or hurls a weak detachment against a powerful one, and neglects to place picked soldiers in the front rank, the result must be ROUT.
[Chang Yu paraphrases the latter part of the sentence and continues: "Whenever there is fighting to be done, the keenest spirits should be appointed to serve in the front ranks, both in order to strengthen the resolution of our own men and to demoralize the enemy." Cf. the primi ordines of Caesar ("De Bello Gallico," V. 28, 44, et al.).]
20. These are six ways of courting defeat, which must be carefully noted by the general who has attained a responsible post.
[See supra, ss. 13.]
21. The natural formation of the country is the soldier's best ally;
[Ch`en Hao says: "The advantages of weather and season are not equal to those connected with ground."]
but a power of estimating the adversary, of controlling the forces of victory, and of shrewdly calculating difficulties, dangers and distances, constitutes the test of a great general.
22. He who knows these things, and in fighting puts his knowledge into practice, will win his battles. He who knows them not, nor practices them, will surely be defeated.
23. If fighting is sure to result in victory, then you must fight, even though the ruler forbid it; if fighting will not result in victory, then you must not fight even at the ruler's bidding.
[Cf. VIII. ss. 3 fin. Huang Shih-kung of the Ch`in dynasty, who is said to have been the patron of Chang Liang and to have written the SAN LUEH, has these words attributed to him: "The responsibility of setting an army in motion must devolve on the general alone; if advance and retreat are controlled from the Palace, brilliant results will hardly be achieved. Hence the god-like ruler and the enlightened monarch are content to play a humble part in furthering their country's cause [lit., kneel down to push the chariot wheel]." This means that "in matters lying outside the zenana, the decision of the military commander must be absolute." Chang Yu also quote the saying: "Decrees from the Son of Heaven do not penetrate the walls of a camp."]
24. The general who advances without coveting fame and retreats without fearing disgrace,
[It was Wellington, I think, who said that the hardest thing of all for a soldier is to retreat.]
whose only thought is to protect his country and do good service for his sovereign, is the jewel of the kingdom.
[A noble presentiment, in few words, of the Chinese "happy warrior." Such a man, says Ho Shih, "even if he had to suffer punishment, would not regret his conduct."]
25. Regard your soldiers as your children, and they will follow you into the deepest valleys; look upon them as your own beloved sons, and they will stand by you even unto death.
[Cf. I. ss. 6. In this connection, Tu Mu draws for us an engaging picture of the famous general Wu Ch`i, from whose treatise on war I have frequently had occasion to quote: "He wore the same clothes and ate the same food as the meanest of his soldiers, refused to have either a horse to ride or a mat to sleep on, carried his own surplus rations wrapped in a parcel, and shared every hardship with his men. One of his soldiers was suffering from an abscess, and Wu Ch`i himself sucked out the virus. The soldier's mother, hearing this, began wailing and lamenting. Somebody asked her, saying: 'Why do you cry? Your son is only a common soldier, and yet the commander-in-chief himself has sucked the poison from his sore.' The woman replied, 'Many years ago, Lord Wu performed a similar service for my husband, who never left him afterwards, and finally met his death at the hands of the enemy. And now that he has done the same for my son, he too will fall fighting I know not where.'" Li Ch`uan mentions the Viscount of Ch`u, who invaded the small state of Hsiao during the winter. The Duke of Shen said to him: "Many of the soldiers are suffering severely from the cold." So he made a round of the whole army, comforting and encouraging the men; and straightway they felt as if they were clothed in garments lined with floss silk.]
26. If, however, you are indulgent, but unable to make your authority felt; kind-hearted, but unable to enforce your commands; and incapable, moreover, of quelling disorder: then your soldiers must be likened to spoilt children; they are useless for any practical purpose.
[Li Ching once said that if you could make your soldiers afraid of you, they would not be afraid of the enemy. Tu Mu recalls an instance of stern military discipline which occurred in 219 A.D., when Lu Meng was occupying the town of Chiang-ling. He had given stringent orders to his army not to molest the inhabitants nor take anything from them by force. Nevertheless, a certain officer serving under his banner, who happened to be a fellow-townsman, ventured to appropriate a bamboo hat belonging to one of the people, in order to wear it over his regulation helmet as a protection against the rain. Lu Meng considered that the fact of his being also a native of Ju-nan should not be allowed to palliate a clear breach of discipline, and accordingly he ordered his summary execution, the tears rolling down his face, however, as he did so. This act of severity filled the army with wholesome awe, and from that time forth even articles dropped in the highway were not picked up.]
27. If we know that our own men are in a condition to attack, but are unaware that the enemy is not open to attack, we have gone only halfway towards victory.
[That is, Ts`ao Kung says, "the issue in this case is uncertain."]
28. If we know that the enemy is open to attack, but are unaware that our own men are not in a condition to attack, we have gone only halfway towards victory.
[Cf. III. ss. 13 (1).]
29. If we know that the enemy is open to attack, and also know that our men are in a condition to attack, but are unaware that the nature of the ground makes fighting impracticable, we have still gone only halfway towards victory.
30. Hence the experienced soldier, once in motion, is never bewildered; once he has broken camp, he is never at a loss.
[The reason being, according to Tu Mu, that he has taken his measures so thoroughly as to ensure victory beforehand. "He does not move recklessly," says Chang Yu, "so that when he does move, he makes no mistakes."]
31. Hence the saying: If you know the enemy and know yourself, your victory will not stand in doubt; if you know Heaven and know Earth, you may make your victory complete.
[Li Ch`uan sums up as follows: "Given a knowledge of three things--the affairs of men, the seasons of heaven and the natural advantages of earth--, victory will invariably crown your battles."]
 See "Pensees de Napoleon 1er," no. 47.
 "The Science of War," chap. 2.
 "Aids to Scouting," p. xii.
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