powerful crossbows into the enemy’s lines.” 2. 行火必有因煙火必素具 In order to carry out an attack with fire, we must have means available. Ts‘ao Kung thinks that 姦人 “traitors in the enemy’s camp” are referred to. He thus takes 因 as the efficient cause only. But Ch‘ên Hao is more likely to be right in saying: 須得其便不獨姦人 “We must have favourable circumstances in general, not merely traitors to help us.” Chia Lin says: 因風燥 “We must avail ourselves of wind and dry weather.” The material for raising fire should always be kept in readiness. 煙火 is explained by Ts‘ao Kung as 燒具 “appliances for making fire.” Tu Mu suggests 艾蒿荻葦薪芻膏油之屬 “dry vegetable matter, reeds, brushwood, straw, grease, oil, etc.” Here we have the material cause. Chang Yü says: 𫎓火之器燃火之物 “vessels for hoarding fire, stuff for lighting fires.” 3. 發火有時起火有日 There is a proper season for making attacks with fire, and special days for starting a conflagration. A fire must not be begun 妄 “recklessly” or 偶然 “at haphazard.” 4. 時者天之燥也日者宿在箕壁翼軫也凡此四宿者風起之日也 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 二十八宮 Twenty-eight Stellar Mansions, corresponding roughly to Sagittarius, Pegasus, Crater and Corvus. The original text, followed by the _T‘u Shu_, has 月 in place of 宿; the present reading rests on the authority of the _T‘ung Tien_ and _Yü Lan_. Tu Mu says: 宿者月之所宿也. For 箕壁, both _T‘ung Tien_ and _Yü Lan_ give the more precise location 戊箕東壁. Mei Yao-ch‘ên tells us that by 箕 is meant the tail of the 龍 Dragon; by 壁, the eastern part of that constellation; by 翼 and 軫, the tail of the 鶉 Quail. for these four are all days of rising wind. 此四宿者 is elliptical for 月在此四宿之日. 蕭繹 Hsiao I (afterwards fourth Emperor of the Liang dynasty, A.D. 552–555) is quoted by Tu Yu as saying that the days 丙丁 of spring, 戊已 of summer, 壬癸 of autumn, and 甲乙 of winter bring fierce gales of wind and rain. 5. 凡火攻必因五火之變而應之 In attacking with fire, one should be prepared to meet five possible developments: I take 五 as qualifying 變, not 火, and therefore think that Chang Yü is wrong in referring 五火 to the five methods of attack set forth in § 1. What follows has certainly nothing to do with these. 6. 火發於內則早應之於外 (1) When fire breaks out inside the enemy’s camp, respond at once The _Yü Lan_ incorrectly reads 軍 for 早. with an attack from without. 7. 火發而其兵靜者待而勿攻 (2) If there is an outbreak of fire, but the enemy’s soldiers remain quiet, bide your time and do not attack. The original text omits 而其. 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. 極其火力可從而從之不可從而止