I should answer, Yes. For the men of Wu and the men of Yüeh are enemies;
[Cf. VI. § 21.]
yet if they are crossing a river in the same boat and are caught by a storm, they will come to each other’s assistance just as the left hand helps the right.
[The meaning is: If two enemies will help each other in a time of common peril, how much more should two parts of the same army, bound together as they are by every tie of interest and fellow-feeling. Yet it is notorious that many a campaign has been ruined through lack of cooperation, especially in the case of allied armies.]
31. Hence it is not enough to put one’s trust in the tethering of horses, and the burying of chariot wheels in the ground.
[These quaint devices to prevent one’s army from running away recall the Athenian hero Sophanes, who carried the anchor with him at the battle of Plataea, by means of which he fastened himself firmly to one spot. [See Herodotus, IX. 74.] It is not enough, says Sun Tzŭ, to render flight impossible by such mechanical means. You will not succeed unless your men have tenacity and unity of purpose, and, above all, a spirit of sympathetic cooperation. This is the lesson which can be learned from the shuai-jan.]
32. The principle on which to manage an army is to set up one standard of courage which all must reach.
[Literally, "level the courage [of all] as though [it were that of] one." If the ideal army is to form a single organic whole, then it follows that the resolution and spirit of its component parts must be of the same quality, or at any rate must not fall below a certain standard. Wellington’s seemingly ungrateful description of his army at Waterloo as "the worst he had ever commanded" meant no more than that it was deficient in this important particular—unity of spirit and courage. Had he not foreseen the Belgian defections and carefully kept those troops in the background, he would almost certainly have lost the day.]
33. How to make the best of both strong and weak—that is a question involving the proper use of ground.
[Mei Yao-ch’en’s paraphrase is: "The way to eliminate the differences of strong and weak and to make both serviceable is to utilize accidental features of the ground." Less reliable troops, if posted in strong positions, will hold out as long as better troops on more exposed terrain. The advantage of position neutralizes the inferiority in stamina and courage. Col. Henderson says: "With all respect to the text books, and to the ordinary tactical teaching, I am inclined to think that the study of ground is often overlooked, and that by no means sufficient importance is attached to the selection of positions… and to the immense advantages that are to be derived, whether you are defending or attacking, from the proper utilization of natural features." [2] ]