If we wish to fight, the enemy can be forced to an engagement even
though he be sheltered behind a high rampart and a deep ditch. All we
need do is to attack some other place that he will be obliged to
relieve.
Tu Mu says: “If the enemy is the invading party, we can cut his
line of communications and occupy the roads by which he will have
to return; if we are the invaders, we may direct our attack
against the sovereign himself.” It is clear that Sun Tzŭ, unlike
certain generals in the late Boer war, was no believer in frontal
attacks.