[Chang Yu, in a quotation from another work, says: "The axiom, that war is based on deception, does not apply only to deception of the enemy. You must deceive even your own soldiers. Make them follow you, but without letting them know why."] By shifting his camp and taking circuitous routes, he prevents the enemy from anticipating his purpose. 38. At the critical moment, the leader of an army acts like one who has climbed up a height and then kicks away the ladder behind him. He carries his men deep into hostile territory before he shows his hand. [Literally, "releases the spring" (see V. § 15), that is, takes some decisive step which makes it impossible for the army to return—like Hsiang Yu, who sunk his ships after crossing a river. Ch’en Hao, followed by Chia Lin, understands the words less well as "puts forth every artifice at his command."] 39. He burns his boats and breaks his cooking-pots; like a shepherd driving a flock of sheep, he drives his men this way and that, and none knows whither he is going. [Tu Mu says: "The army is only cognizant of orders to advance or retreat; it is ignorant of the ulterior ends of attacking and conquering."] 40. To muster his host and bring it into danger:—this may be termed the business of the general. [Sun Tzŭ means that after mobilization there should be no delay in aiming a blow at the enemy’s heart. Note how he returns again and again to this point. Among the warring states of ancient China, desertion was no doubt a much more present fear and serious evil than it is in the armies of today.] 41. The different measures suited to the nine varieties of ground; [Chang Yu says: "One must not be hide-bound in interpreting the rules for the nine varieties of ground."] the expediency of aggressive or defensive tactics; and the fundamental laws of human nature: these are things that must most certainly be studied. 42. When invading hostile territory, the general principle is, that penetrating deeply brings cohesion; penetrating but a short way means dispersion. [Cf. _supra_, § 20.] 43. When you leave your own country behind, and take your army across neighbourhood territory, you find yourself on critical ground. [This "ground" is curiously mentioned in VIII. § 2, but it does not figure among the Nine Situations or the Six Calamities in chap. X. One’s first impulse would be to translate it distant ground," but this, if we can trust the commentators, is precisely what is not meant here. Mei Yao-ch’en says it is "a position not far enough advanced to be called ‘facile,’ and not near enough to home to be ‘dispersive,’ but something between the two." Wang Hsi says: "It is ground separated from home by an interjacent state, whose territory we have had to cross in order to reach it. Hence, it is incumbent on us to settle our business there quickly." He adds that this position is of rare occurrence, which is the reason why it is not included among the Nine Situations.]