observing signs of the enemy. Pass quickly over mountains, and keep in
the neighbourhood of valleys.
[The idea is, not to linger among barren uplands, but to keep close to
supplies of water and grass. Cf. Wu Tzŭ, ch. 3: "Abide not in natural
ovens," i.e. "the openings of valleys." Chang Yu tells the following
anecdote: Wu-tu Ch’iang was a robber captain in the time of the Later
Han, and Ma Yuan was sent to exterminate his gang. Ch’iang having found
a refuge in the hills, Ma Yuan made no attempt to force a battle, but
seized all the favourable positions commanding supplies of water and
forage. Ch’iang was soon in such a desperate plight for want of
provisions that he was forced to make a total surrender. He did not
know the advantage of keeping in the neighbourhood of valleys."]