rangements and changing his plans,

[Wang Hsi thinks that this means not using the same
stratagem twice.]

he keeps the enemy without definite knowledge.

[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. ss. 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 nothing 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 Tzu 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, ss. 20.]

43. When you leave your own country behind, and take your
army across neighborhood territory, you find yourself on critical
grou