(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
favourable 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, 若敵居荒澤草穢或營栅可焚之地卽須及時發火不必更待內發作然後應之恐
敵人自燒野草我起火無益 “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 wait 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 李陵 Li Ling once
baffled the 單于 leader of the Hsiung-nu in this way. The latter,
taking advantage of a favourable wind, tried to set fire to the
Chinese general’s camp, but found that every scrap of combustible
vegetation in the neighbourhood had already been burnt down. On
the other hand, 波才 Po-ts‘ai, a general of the 黃巾賊 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 長社 Ch‘ang-shê, which was held by 皇甫嵩 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 Tzŭ, V. §§ 5, 6 and 10.] Now the rebels have pitched
their camp in the midst of thick grass (依草結營), 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, f. 2 _r_^o.]