1. Sun Tzŭ said: The art of war recognises nine varieties of ground: (1) Dispersive ground; (2) facile ground; (3) contentious ground; (4) open ground; (5) ground of intersecting highways; (6) serious ground; (7) difficult ground; (8) hemmed-in ground; (9) desperate ground. 2. When a chieftain is fighting in his own territory, it is dispersive ground. [So called because the soldiers, being near to their homes and anxious to see their wives and children, are likely to seize the opportunity afforded by a battle and scatter in every direction. "In their advance," observes Tu Mu, "they will lack the valor of desperation, and when they retreat, they will find harbors of refuge."] 3. When he has penetrated into hostile territory, but to no great distance, it is facile 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 Tzŭ, 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 Tzŭ-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.