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