ile ground.

[Li Ch`uan and Ho Shih say "because of the facility for
retreating," and the other commentators give similar
explanations. Tu Mu remarks: "When your army has crossed the
border, you should burn your boats and bridges, in order to make
it clear to everybody that you have no hankering after home."]

4. Ground the possession of which imports great advantage
to either side, is contentious ground.

[Tu Mu defines the ground as ground "to be contended for."
Ts`ao Kung says: "ground on which the few and the weak can
defeat the many and the strong," such as "the neck of a pass,"
instanced by Li Ch`uan. Thus, Thermopylae was of this
classification because the possession of it, even for a few days
only, meant holding the entire invading army in check and thus
gaining invaluable time. Cf. Wu Tzu, ch. V. ad init.: "For
those who have to fight in the ratio of one to ten, there is
nothing better than a narrow pass." When Lu Kuang was returning
from his triumphant expedition to Turkestan in 385 A.D., and had
got as far as I-ho, laden with spoils, Liang Hsi, administrator
of Liang-chou, taking advantage of the death of Fu Chien, King of
Ch`in, plotted against him and was for barring his way into the
province. Yang Han, governor of Kao-ch`ang, counseled him,
saying: "Lu Kuang is fresh from his victories in the west, and
his soldiers are vigorous and mettlesome. If we oppose him in
the shifting sands of the desert, we shall be no match for him,
and we must therefore try a different plan. Let us hasten to
occupy the defile at the mouth of the Kao-wu pass, thus cutting
him off from supplies of water, and when his troops are
prostrated with thirst, we can dictate our own terms without
moving. Or if you think that the pass I mention is too far off,
we could make a stand against him at the I-wu pass, which is
nearer. The cunning and resource of Tzu-fang himself would be
expended in vain against the enormous strength of these two
positions." Liang Hsi, refusing to act on this advice, was
overwhelmed and swept away by the invader.]

5. Ground on which each side has liberty of movement is
open ground.

[There are various interpretations of the Chinese adjective
for this type of ground. Ts`ao Kung says it means "ground
covered with a network of roads," like a chessboard. Ho Shih
suggested: "ground on which intercommunication is easy."]

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