re 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 per