10. In battle, there are not more than two methods of attack — the direct and the indirect; yet these two in combination give rise to an endless series of manœuvres.
11. The direct and the indirect lead on to each other in turn. It is like moving in a circle — you never come to an end. Who can exhaust the possibilities of their combination?
The T‘u Shu adds 哉. The final 之 may refer either to the circle or, more probably, to the 奇正之變 understood. Capt. Calthrop is wrong with: “They are a mystery that none can penetrate.”
12. The onset of troops is like the rush of a torrent which will even roll stones along in its course.
13. The quality of decision is like the well-timed swoop of a falcon which enables it to strike and destroy its victim.
For 疾 the Yü Lan reads 擊, which is also supported by a quotation in the 呂氏春秋 [3rd cent. B.C.]. 節 in this context is a word which really defies the best efforts of the translator. Tu Mu says that it is equivalent to 節量遠近 “the measurement or estimation of distance.” But this meaning does not quite fit the illustrative simile in §15. As applied to the falcon, it seems to me to denote that instinct of self-restraint which keeps the bird from swooping on its quarry until the right moment, together with the power of judging when the right moment has arrived. The analogous quality in soldiers is the highly important one of being able to reserve their fire until the very instant at which it will be most effective. When the “Victory” went into action at Trafalgar at hardly more than drifting pace, she was for several minutes exposed to a storm of shot and shell before replying with a single gun. Nelson coolly waited until he was within close range, when the broadside he brought to bear worked fearful havoc on the enemy’s nearest ships. That was a case of 節.