When there are means of communication on all four sides, the ground is one of intersecting highways. 44. When you penetrate deeply into a country, it is serious ground. When you penetrate but a little way, it is facile ground. 45. When you have the enemy’s strongholds on your rear, and narrow passes in front, it is hemmed-in ground. When there is no place of refuge at all, it is desperate ground. 46. Therefore, on dispersive ground, I would inspire my men with unity of purpose. [This end, according to Tu Mu, is best attained by remaining on the defensive, and avoiding battle. Cf. _supra_, § 11.] On facile ground, I would see that there is close connection between all parts of my army. [As Tu Mu says, the object is to guard against two possible contingencies: "(1) the desertion of our own troops; (2) a sudden attack on the part of the enemy." Cf. VII. § 17. Mei Yao-ch’en says: "On the march, the regiments should be in close touch; in an encampment, there should be continuity between the fortifications."] 47. On contentious ground, I would hurry up my rear. [This is Ts’ao Kung’s interpretation. Chang Yu adopts it, saying: "We must quickly bring up our rear, so that head and tail may both reach the goal." That is, they must not be allowed to straggle up a long way apart. Mei Yao-ch’en offers another equally plausible explanation: "Supposing the enemy has not yet reached the coveted position, and we are behind him, we should advance with all speed in order to dispute its possession." Ch’en Hao, on the other hand, assuming that the enemy has had time to select his own ground, quotes VI. § 1, where Sun Tzŭ warns us against coming exhausted to the attack. His own idea of the situation is rather vaguely expressed: "If there is a favourable position lying in front of you, detach a picked body of troops to occupy it, then if the enemy, relying on their numbers, come up to make a fight for it, you may fall quickly on their rear with your main body, and victory will be assured." It was thus, he adds, that Chao She beat the army of Ch’in. (See p. 57.)] 48. On open ground, I would keep a vigilant eye on my defences. On ground of intersecting highways, I would consolidate my alliances. 49. On serious ground, I would try to ensure a continuous stream of supplies. [The commentators take this as referring to forage and plunder, not, as one might expect, to an unbroken communication with a home base.] On difficult ground, I would keep pushing on along the road. 50. On hemmed-in ground, I would block any way of retreat.