So much for mountain warfare.
After 山, the T‘ung Tien and Yü Lan insert 谷.
3. 絶水必遠水
After crossing a river, you should get far away from it.
“In order to tempt the enemy to cross after you,” according to Ts‘ao Kung, and also, says Chang Yü, “in order not to be impeded in your evolutions.” The T‘ung Tien reads 敵若絶水 “If the enemy crosses a river,” etc. But in view of the next sentence, this is almost certainly an interpolation.
4. 客絶水而來勿迎之於水內令半濟而擊之利
When an invading force crosses a river in its onward march, do not advance to meet it in mid-stream. It will be best to let half the army get across, and then deliver your attack.
The T‘ung Tien and Yü Lan read 度 for 濟, without change of meaning. Wu Tzŭ plagiarises this passage twice over:—ch. II ad fin., 涉水半渡可擊; ch. V, 敵若絶水半渡而擊. Li Ch‘üan alludes to the great victory won by Han Hsin over 龍且 Lung Chü at the 濰 Wei River. Turning to the Ch‘ien Han Shu, ch. 34, fol. 6 verso, we find the battle described as follows: “The two armies were drawn up on opposite sides of the river. In the night, Han Hsin ordered his men to take some ten thousand sacks filled with sand and construct a dam a little higher up. Then, leading half his army across, he attacked Lung Chü; but after a time, pretending to have failed in his attempt, he hastily withdrew to the other bank. Lung Chü was much elated by this unlooked-for success, and exclaiming: “I felt sure that Han Hsin was really a coward!” he pursued him and began crossing the river in his turn. Han Hsin now sent a party to cut open the sandbags, thus releasing a great volume of water, which swept down and prevented the greater portion of Lung Chü’s army from getting across. He then turned upon the force which had been cut off, and annihilated it, Lung Chü himself being amongst the slain. The rest of the army, on the further bank, also scattered and fled in all directions.”
5. 欲戰者無附於水而迎客
If you are anxious to fight, you should not go to meet the invader near a river which he has to cross.