The skilled commanders of the past first made themselves invulnerable, then waited for the enemy’s moment of vulnerability. Invulnerability depends on one’s own efforts, whereas victory over the enemy depends on the latter’s negligence. It follows that those skilled in warfare can make themselves invincible but they cannot be sure of victory over the enemy. Therefore it is said that victory can be anticipated but it cannot be forced.
Invulnerability lies with defense, and opportunity of victory with attack. One defends when his strength is inadequate; he attacks when his strength is abundant. He who is skilled in defense positions his forces in places as safe and inaccessible as in the depth of the earth, whereas he who is skilled in attack strikes as from the highest reaches of heaven. In this way he is able both to protect himself and to win complete victory.
To foresee a victory which is within the ken of the ordinary people is not the acme of excellence. Neither is it the acme of excellence when one is acclaimed universally for winning a fierce battle. It is like lifting a strand of animal hair in autumn (tr.: Animal hair is very fine and light in autumn.), which is no sign of strength; like being able to see the sun and the moon, which is no test of vision; like hearing a thunderclap, which is no indication of hearing ability. What the ancients called a master of war is one who overpowers an enemy easy to defeat. The victories won by a master of war gain him neither fame for his wisdom nor merit for his valor, because he is bound to win as his tactics are built on assurances of victory. He defeats an enemy already defeated. Thus, the skilled warrior puts himself in a position in which he cannot be defeated and misses no opportunity to defeat his enemy.
So it is that a victorious army will not engage the enemy unless it is assured of the necessary conditions for victory, whereas an army destined to defeat rushes into battle in the hope that it will win by luck. The skilled warrior seeks victory by cultivating the way and strengthening rules and regulations, and in so doing, gains the initiative over his enemy.
The five elements mentioned in The Rules of War are: 1) measurement of space, 2) estimation of quantity, 3) calculation of number, 4) comparison of strength, and 5) assessment of chances of victory. Measurement of space refers to the difference in the territories of the opposing parties; from that derives estimation of quantity, which refers to the difference in resources; from that, calculation of numbers, which refers to the difference in the size of their troops; from that, comparison of the relative strengths of their armies and finally, assessment of the material base for the chances of victory.
Thus, a victorious army has full advantage over its enemy, just like pitting 500 grains against one grain; the opposite is true with an army doomed to defeat, like pitting one against 500. So great is the disparity of strength that a victorious army goes into battle with the force of an onrushing torrent which, when suddenly released, plunges into a chasm a thousand fathoms deep. This is what we mean by disposition.