4. The proper season is when the weather is very dry; the special days are those when the moon is in the constellations of the Sieve, the Wall, the Wing or the Cross-bar;
[These are, respectively, the 7th, 14th, 27th, and 28th of the Twenty-eight Stellar Mansions, corresponding roughly to Sagittarius, Pegasus, Crater and
for these four are all days of rising wind.
5. In attacking with fire, one should be prepared to meet five possible developments:
6. (1) When fire breaks out inside to enemy's camp, respond at once with an attack from without.
7. (2) If there is an outbreak of fire, but the enemy's soldiers remain quiet, bide your time and do not attack.
[The prime object of attacking with fire is to throw the enemy into confusion. If this effect is not produced, it means that the enemy is ready to receive us. Hence the necessity for caution.]
8. (3) When the force of the flames has reached its height, follow it up with an attack, if that is practicable; if not, stay where you are.
[Ts`ao Kung says: "If you see a possible way, advance; but if you find the difficulties too great, retire."]
9. (4) If it is possible to make an assault with fire from without, do not wait for it to break out within, but deliver your attack at a favorable moment.
[Tu Mu says that the previous paragraphs had reference to the fire breaking out (either accidentally, we may suppose, or by the agency of incendiaries) inside the enemy's camp. "But," he continues, "if the enemy is settled in a waste place littered with quantities of grass, or if he has pitched his camp in a position which can be burnt out, we must carry our fire against him at any seasonable opportunity, and not await on in hopes of an outbreak occurring within, for fear our opponents should themselves burn up the surrounding vegetation, and thus render our own attempts fruitless." The famous Li Ling once baffled the leader of the Hsiung-nu in this way. The latter, taking advantage of a favorable wind, tried to set fire to the Chinese general's camp, but found that every scrap of combustible vegetation in the neighborhood had already been burnt down. On the other hand, Po-ts`ai, a general of the Yellow Turban rebels, was badly defeated in 184 A.D. through his neglect of this simple precaution. "At the head of a large army he was besieging Ch`ang-she, which was held by Huang-fu Sung. The garrison was very small, and a general feeling of nervousness pervaded the ranks; so Huang-fu Sung called his officers together and said: "In war, there are various indirect methods of attack, and numbers do not count for everything. [The commentator here quotes Sun Tzu, V. SS. 5, 6 and 10.] Now the rebels have pitched their camp in the midst of thick grass which will easily burn when the wind blows. If we set fire to it at night, they will be thrown into a panic, and we can make a sortie and attack them on all sides at once, thus emulating the achievement of T`ien Tan.' [See p. 90.] That same evening, a strong breeze sprang up; so Huang-fu Sung instructed his soldiers to bind reeds together into torches and mount guard on the city walls, after which he sent out a band of daring men, who stealthily made their way through the lines and started the fire with loud shouts and yells. Simultaneously, a glare of light shot up from the city walls, and Huang-fu Sung, sounding his drums, led a rapid charge, which threw the rebels into confusion and put them to headlong flight." [HOU HAN SHU, ch. 71.] ]
10. (5) When you start a fire, be to windward of it. Do not attack from the leeward.
[Chang Yu, following Tu Yu, says: "When you make a fire, the enemy will retreat away from it; if you oppose his retreat and attack him then, he will fight desperately, which will not conduce to your success." A rather more obvious explanation is given by Tu Mu: "If the wind is in the east, begin burning to the east of the enemy, and follow up the attack yourself from that side. If you start the fire on the east side, and then attack from the west, you will suffer in the same way as your enemy."]
11. A wind that rises in the daytime lasts long, but a night breeze soon falls.
[Cf. Lao Tzu's saying: "A violent wind does not last the space of a morning." (TAO TE CHING, chap. 23.) Mei Yao-ch`en and Wang Hsi say: "A day breeze dies down at nightfall, and a night breeze at daybreak. This is what happens as a general rule." The phenomenon observed may be correct enough, but how this sense is to be obtained is not apparent.]
12. In every army, the five developments connected with fire must be known, the movements of the stars calculated, and a watch kept for the proper days.
[Tu Mu says: "We must make calculations as to the paths of the stars, and watch for the days on which wind will rise, before making our attack with fire." Chang Yu seems to interpret the text differently: "We must not only know how to assail our opponents with fire, but also be on our guard against similar attacks from them."]
13. Hence those who use fire as an aid to the attack show intelligence; those who use water as an aid to the attack gain an accession of strength.
14. By means of water, an enemy may be intercepted, but not robbed of all his belongings.
[Ts`ao Kung's note is: "We can merely obstruct the enemy's road or divide his army, but not sweep away all his accumulated stores." Water can do useful service, but it lacks the terrible destructive power of fire. This is the reason, Chang Yu concludes, why the former is dismissed in a couple of sentences, whereas the attack by fire is discussed in detail. Wu Tzu (ch. 4) speaks thus of the two elements: "If an army is encamped on low-lying marshy ground, from which the water cannot run off, and where the rainfall is heavy, it may be submerged by a flood. If an army is encamped in wild marsh lands thickly overgrown with weeds and brambles, and visited by frequent gales, it may be exterminated by fire."]
15. Unhappy is the fate of one who tries to win his battles and succeed in his attacks without cultivating the spirit of enterprise; for the result is waste of time and general stagnation.
[This is one of the most perplexing passages in Sun Tzu. Ts`ao Kung says: "Rewards for good service should not be deferred a single day." And Tu Mu: "If you do not take opportunity to advance and reward the deserving, your subordinates will not carry out your commands, and disaster will ensue." For several reasons, however, and in spite of the formidable array of scholars on the other side, I prefer the interpretation suggested by Mei Yao-ch`en alone, whose words I will quote: "Those who want to make sure of succeeding in their battles and assaults must seize the favorable moments when they come and not shrink on occasion from heroic measures: that is to say, they must resort to such means of attack of fire, water and the like. What they must not do, and what will prove fatal, is to sit still and simply hold to the advantages they have got."]
16. Hence the saying: The enlightened ruler lays his plans well ahead; the good general cultivates his resources.
[Tu Mu quotes the following from the SAN LUEH, ch. 2: "The warlike prince controls his soldiers by his authority, kits them together by good faith, and by rewards makes them serviceable. If faith decays, there will be disruption; if rewards are deficient, commands will not be respected."]
17. Move not unless you see an advantage; use not your troops unless there is something to be gained; fight not unless the position is critical.
[Sun Tzu may at times appear to be over-cautious, but he never goes so far in that direction as the remarkable passage in the TAO TE CHING, ch. 69. "I dare not take the initiative, but prefer to act on the defensive; I dare not advance an inch, but prefer to retreat a foot."]
18. No ruler should put troops into the field merely to gratify his own spleen; no general should fight a battle simply out of pique.
19. If it is to your advantage, make a forward move; if not, stay where you are.
[This is repeated from XI. ss. 17. Here I feel convinced that it is an interpolation, for it is evident that ss. 20 ought to follow immediately on
20. Anger may in time change to gladness; vexation may be succeeded by content.
21. But a kingdom that has once been destroyed can never come again into being;
[The Wu State was destined to be a melancholy example of this saying.]
nor can the dead ever be brought back to life.
22. Hence the enlightened ruler is heedful, and the good general full of caution. This is the way to keep a country at peace and an army intact.
 "Unless you enter the tiger's lair, you cannot get hold of the tiger's cubs."