(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: 見可而進知難而退 “If you see a possible way, advance; but if you find the difficulties too great, retire.” 9. 火可發於外無待於內以時發之 (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.] 10. 火發上風無攻下風 (5) When you start a fire, be to windward of it. Do not attack from the leeward.