I have departed slightly from the traditional interpretation of Ts`ao Kung, who says: "From the time of receiving the sovereign's instructions until our encampment over against the enemy, the tactics to be pursued are most difficult." It seems to me that the tactics or maneuvers can hardly be said to begin until the army has sallied forth and encamped, and Ch`ien Hao's note gives color to this view: "For levying, concentrating, harmonizing and entrenching an army, there are plenty of old rules which will serve. The real difficulty comes when we engage in tactical operations." Tu Yu also observes that "the great difficulty is to be beforehand with the enemy in seizing favorable position."
This sentence contains one of those highly condensed and somewhat enigmatical expressions of which Sun Tzu is so fond. This is how it is explained by Ts`ao Kung: "Make it appear that you are a long way off, then cover the distance rapidly and arrive on the scene before your opponent." Tu Mu says: "Hoodwink the enemy, so that he may be remiss and leisurely while you are dashing along with utmost speed." Ho Shih gives a slightly different turn: "Although you may have difficult ground to traverse and natural obstacles to encounter this is a drawback which can be turned into actual advantage by celerity of movement." Signal examples of this saying are afforded by the two famous passages across the Alps—that of Hannibal, which laid Italy at his mercy, and that of Napoleon two thousand years later, which resulted in the great victory of Marengo.