9. O divine art of and secrecy! Through you we learn to be invisible, through you inaudible;
Literally, “without form or sound,” but it is said of course with reference to the enemy. Chang Yü, whom I follow, draws no sharp distinction between 微 and 神, but Tu Mu and others think that 微 indicates the secrecy to be observed on the defensive, and 神 the rapidity to be displayed in attack. The Yü Lan text differs considerably from ours, reading: 微乎微乎故能隱於常形神乎神乎故能爲敵司命.
and hence we can hold the enemy's fate in our hands.
The T‘ung Tien has 故能爲變化司命. Capt. Calthrop’s version of this paragraph is so remarkable that I cannot refrain from quoting it in full: “Now the secrets of the art of offence are not to be easily apprehended, as a certain shape or noise can be understood, of the senses; but when these secrets are once learnt, the enemy is mastered.”
10. You may advance and be absolutely irresistible, if you make for the enemy's weak points; you may retire and be safe from pursuit if your movements are more rapid than those of the enemy.
The second member of the sentence is weak, because 不可及 is nearly tautologous with 不可追. The Yü Lan reads 遠 for 速.
11. If we wish to fight, the enemy can be forced to an engagement even though he be sheltered behind a high rampart and a deep ditch. All we need do is attack some other place that he will be obliged to relieve.
Tu Mu says: “If the enemy is the invading party, we can cut his line of communications and occupy the roads by which he will have to return; if we are the invaders, we may direct our attack against the sovereign himself.” It is clear that Sun Tzŭ, unlike certain generals in the later Boer war, was no believer in frontal attacks.