[Cf. Lao Tzŭ’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 Tzŭ (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 Tzŭ. 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 favourable 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.