The Art of War by active 6th century B.C. Sunzi

23. Thus the energy developed by good fighting men is as the momentum

of a round stone rolled down a mountain thousands of feet in height. So much on the subject of energy. [The chief lesson of this chapter, in Tu Mu’s opinion, is the paramount importance in war of rapid evolutions and sudden rushes. "Great results," he adds, "can thus be achieved with small forces."] [1] "Forty-one Years in India," chapter 46.