Master Sun says the skilled general of old first ensures his own strength, then waits for the enemy’s weakness. His strength is his responsibility and the enemy’s weakness is the enemy’s responsibility, never the other way around. This is why it is said it is possible to know victory but not achieve it.
A general cannot create a weakness in the enemy out of thin air. Instead, he exploits any and every opportunity that presents itself, and actively intensifies any weakness he can spy in the enemy ranks. So, if no weakness presents itself, the general must fall back on his own strength to see him through.
Invulnerability is about defense, while vulnerability is about attack. The first suggests a lack, while the latter suggests plenty. A good defender knows how to move as though he is under the earth, while the skilful attacker comes as though he advanced above heaven. This is how they protect themselves and win.
Vulnerable/invulnerable, defense/attack, lack/plenty, under the earth/above the heavens—Sun describes his approach to war in terms of opposing forces that complement and give rise to each other, meaning Yin and Yang. In creating a strong defense, the general makes himself invulnerable. In attacking the enemy, the general causes his foe to be vulnerable. Skilled in defense, he hides so well it is like he is underground (perhaps in reality under the cover of forest), while he attacks so swiftly it is like he flew on the clouds like the heroes of old.
Common people can see an ordinary victory. To be recognized as a victor does not show true skill. Lifting autumn fur doesn’t show strength. Seeing the sun and the moon doesn’t mean you are perceptive. Hearing thunder doesn’t reveal a good sense of hearing. The heroes of old won easy victories.
The subtleties of war are beyond what the layperson can see. Sun gives poetic examples of stating the obvious. Generals must be a cut above such perceptive prowess. They must see into the nature of things before they even happen, with wisdom that will outmaneuver the enemy.
A skillful general’s victories do not win him fame or honor. His victories are flawless, because they are inevitable. He beats an already defeated enemy. He takes strong ground and pounces on every opportunity. Victorious armies don’t seek out battles first, but seek first victory. The opposite is true for defeated armies. The general who is skilled in strategy keeps the Way and the law, so he is master of victory and defeat.
The wise general’s battles are won offstage. If the perfect victory is won without ever doing battle, it is less likely to make its way into the history books. The common people love grand tales of battlefield heroism, but the true leader wins quick, decisive conflicts that might not even make it to the battlefield at all. Meanwhile, those who seek out glory and renown are more likely to fail, as they pursue the wrong goals. In referring to the Way as connected with being skilled in strategy, Sun invokes the traditional idea that an honorable leader earns his total authority.
There are five steps to war: measuring, estimating, calculating, comparing, and then victory. Earth leads to measurement, which in turn leads to estimating, then to calculating, comparison, and victory. The army that wins is like a heavy weight crushing a single grain. The opposite is true for a defeated army. The victors are like water smashing through a gorge. It is all about forms and dispositions.
Studying, understanding, and scheming are the keys to victory. By knowing the enemy, terrain, and all other aspects of the upcoming battle in minute detail, the general can throw his men into the fray with certainty of success. Sun asserts this is a natural law, as obvious as crushing a tiny grain with a large stone. If the general understands the nature of his men, their “Forms and / Dispositions,” he can engineer the situation to release their innate power like a waterfall, crushing the enemy army. For example, if his army is mostly made up of chariots, he would seek a battleground with clear and even terrain, so their full fury could be unleashed.