. As
soon as the whole army had passed by, the hidden troops fell on
his rear, while Ts`ao himself turned and met his pursuers in
front, so that they were thrown into confusion and annihilated.
Ts`ao Ts`ao said afterwards: "The brigands tried to check my
army in its retreat and brought me to battle in a desperate
position: hence I knew how to overcome them."]

36. When you surround an army, leave an outlet free.

[This does not mean that the enemy is to be allowed to
escape. The object, as Tu Mu puts it, is "to make him believe
that there is a road to safety, and thus prevent his fighting
with the courage of despair." Tu Mu adds pleasantly: "After
that, you may crush him."]

Do not press a desperate foe too hard.

[Ch`en Hao quotes the saying: "Birds and beasts when
brought to bay will use their claws and teeth." Chang Yu says:
"If your adversary has burned his boats and destroyed his
cooking-pots, and is ready to stake all on the issue of a battle,
he must not be pushed to extremities." Ho Shih illustrates the
meaning by a story taken from the life of Yen-ch`ing. That
general, together with his colleague Tu Chung-wei was surrounded
by a vastly superior army of Khitans in the year 945 A.D. The
country was bare and desert-like, and the little Chinese force
was soon in dire straits for want of water. The wells they bored
ran dry, and the men were reduced to squeezing lumps of mud and
sucking out the moisture. Their ranks thinned rapidly, until at
last Fu Yen-ch`ing exclaimed: "We are desperate men. Far better
to die for our country than to go with fettered hands into
captivity!" A strong gale happened to be blowing from the
northeast and darkening the air with dense clouds of sandy dust.
To Chung-wei was for waiting until this had abated before
deciding on a final attack; but luckily another officer, Li Shou-
cheng by name, was quicker to see an opportunity, and said:
"They are many and we are few, but in the midst of this sandstorm
our numbers will not be discernible; victory will go to the
strenuous fighter, and the wind will be our best ally."
Accordingly, Fu Yen-ch`ing made a sudden and wholly unexpected
onslaught with his cavalry, routed the barbarians and succeeded
in breaking through to safety.]

37. Such is the art of warfare.

[1] See Col. Henderson, op. cit. vol. I. p. 426.

[2] For a number of maxims on this head, see "Marshal Turenne"
(Longmans,