According as circumstances are favourable, one should modify one’s
plans.
Sun Tzŭ, as a practical soldier, will have none of the “bookish
theoric.” He cautions us here not to pin our faith to abstract
principles; “for,” as Chang Yü puts it, “while the main laws of
strategy can be stated clearly enough for the benefit of all and
sundry, you must be guided by the actions of the enemy in attempting
to secure a favourable position in actual warfare.” On the eve of the
battle of Waterloo, Lord Uxbridge, commanding the cavalry, went to the
Duke of Wellington in order to learn what his plans and calculations
were for the morrow, because, as he explained, he might suddenly find
himself Commander-in-chief and would be unable to frame new plans in a
critical moment. The Duke listened quietly and then said: “Who will
attack the first to-morrow—I or Bonaparte?” “Bonaparte,” replied Lord
Uxbridge. “Well,” continued the Duke, “Bonaparte has not given me any
idea of his projects; and as my plans will depend upon his, how can
you expect me to tell you what mine are?”[168]