19. Thus one who is skilful at keeping the enemy on the move maintains deceitful appearances, according to which the enemy will act. He sacrifices something, that the enemy may snatch at it. 20. By holding out baits, he keeps him on the march; then with a body of picked men he lies in wait for him. 21. The clever combatant looks to the effect of combined energy, and does not require too much from individuals. Hence his ability to pick out the right men and utilise combined energy. 22. When he utilises combined energy, his fighting men become as it were like unto rolling logs or stones. For it is the nature of a log or stone to remain motionless on level ground, and to move when on a slope; if four-cornered, to come to a standstill, but if round-shaped, to go rolling down. 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. VI. WEAK POINTS AND STRONG 1. Sun Tzŭ said: Whoever is first in the field and awaits the coming of the enemy, will be fresh for the fight; whoever is second in the field and has to hasten to battle, will arrive exhausted. 2. Therefore the clever combatant imposes his will on the enemy, but does not allow the enemy’s will to be imposed on him. 3. By holding out advantages to him, he can cause the enemy to approach of his own accord; or, by inflicting damage, he can make it impossible for the enemy to draw near. 4. If the enemy is taking his ease, he can harass him; if well supplied with food, he can starve him out; if quietly encamped, he can force him to move. 5. Appear at points which the enemy must hasten to defend; march swiftly to places where you are not expected. 6. An army may march great distances without distress, if it marches through country where the enemy is not. 7. You can be sure of succeeding in your attacks if you only attack places which are undefended.You can ensure the safety of your defence if you only hold positions that cannot be attacked. 8. Hence that general is skilful in attack whose opponent does not know what to defend; and he is skilful in defence whose opponent does not know what to attack. 9. O divine art of subtlety and secrecy! Through you we learn to be invisible, through you inaudible; and hence we can hold the enemy’s fate in our hands. 10. You may advance and be absolutely irresistible, if you make for the enemy’s weak points; you may retire and be safe from pursuit if your movements are more rapid than those of the enemy. 11. 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 attack some other place that he will be obliged to relieve. 12. If we do not wish to fight, we can prevent the enemy from engaging us even though the lines of our encampment be merely traced out on the ground. All we need do is to throw something odd and unaccountable in his way.