the fifth is to hurl dropping fire amongst the enemy.
[Tu Yu says in the T’ung Tien: "To drop fire into the enemy’s camp. The method by which this may be done is to set the tips of arrows alight by dipping them into a brazier, and then shoot them from powerful crossbows into the enemy’s lines."]
- In order to carry out an attack, we must have means available.
[T’sao Kung thinks that "traitors in the enemy’s camp" are referred to. But Ch’en Hao is more likely to be right in saying: "We must have favourable circumstances in general, not merely traitors to help us." Chia Lin says: "We must avail ourselves of wind and dry weather."]
the material for raising fire should always be kept in readiness.
[Tu Mu suggests as material for making fire: "dry vegetable matter, reeds, brushwood, straw, grease, oil, etc." Here we have the material cause. Chang Yu says: "vessels for hoarding fire, stuff for lighting fires."]
- There is a proper season for making attacks with fire, and special days for starting a conflagration.
- 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 Twenty-eight Stellar Mansions, corresponding roughly to Sagittarius, Pegasus, Crater and Corvus.]
for these four are all days of rising wind.
- In attacking with fire, one should be prepared to meet five possible developments: