Chapter IV is quite short, but is of profound importance. The lesson that this chapter teaches can be summarized as: victorious warriors win first and then go to war, while defeated warriors go to war and then seek to win.
1. Anciently the skillful warriors first made themselves invincible and awaited the enemy's moment of vulnerability.
2. Invincibility depends on one's self; the enemy's vulnerability on him.
3. It follows that those skilled in war can make themselves invincible but cannot cause an enemy to be certainly vulnerable.
4. Therefore it is said that one may know how to win, but cannot necessarily do so.
Ah, yet another of Sun Tzu's lessons that has been driven home by countless hours of Civilization IV. This is pretty self-explanatory; yet another reiteration of 'attack when you are strong and your enemy is weak,' but to summarize: do what you can to mitigate attacks against you and expect the enemy to do the same. Therefore seize opportunities to attack whenever they present themselves; no one is invincible all the time. Better still, strive to create circumstances that will increase the enemies vulnerability.
5. Invincibility lies in the defence; the possibility of victory in the attack.
6. One defends when his strength is inadequate; he attacks when it is abundant.
7. The experts in defence conceal themselves as under the ninefold earth; those skilled in attack move as from above the ninefold heavens. Thus they are capable both of protecting themselves and of gaining a complete victory.
Take advantage of terrain features to aid in your defence and attack. When defending try to position yourself around a choke point to limit the number of attackers that assault you and prevent them from outflanking you. This is a tactic that, I think, most players have an intuitive grasp of. Whenever my players are badly outnumbered they try, whenever possible, to defend doorways or narrow passages, restricting the number of enemies that can attack at once, thus eliminating their numerical advantage.
I interpret 'attacking as from above the ninefold heavens' as emphasizing the importance of seizing high ground. Employing missile fire while your enemies are trying to climb up to your position is a great way to thin out the ranks a bit before entering melee. You might even force them to make a morale check and flee, allowing you to cut them down from behind as they run.
8. To foresee a victory which the ordinary man can foresee is not the acme of skill;
9. To triumph in battle and be universally acclaimed 'Expert' is no the acme of skill, for to lift an autumn down requires no great strength; to distinguish between the sun and moon is no test of vision; to hear the thunderclap is no indication of acute hearing.
10. Anciently those called skilled in war conquered an enemy easily conquered.
11. And therefore the victories won by a master of war gain him neither reputation for wisdom nor merit for valour.
These passages are a bit obtuse, but I think what Sun Tzu is getting at is that Warlords who have won mighty battles gain a reputation for excellence that is largely undeserved because their victories were easily obtained. They seem impressive only to the untrained. The true master of war garners no reputation because his victories are far more subtle and he wins his wars by defeating his opponent without ever needing to fight and to the untrained observer it would appear that he did nothing at all.
12. For he wins his victories without erring. 'Without erring' means that whatever he does insures his victory; he conquers an enemy already defeated.
13. Therefore the skillful commander takes up a position in which he cannot be defeated and misses no opportunity to master his enemy.
14. Thus a victorious army wins its victories before seeking battle; an army destined to defeat fights in the hope of winning.
Finally we get to the meat of the matter and how we can apply this lesson to our gaming strategy: attack only when victory is already assured. This might seem obvious, but how often do characters charge into a fight without knowing exactly what they are getting into or how they will win? All too often they rely on lucky dice rolls to win the day, and we all know how fickle fortune can be. There are days when I'm sitting behind my screen rolling a shocking string of high 'to hit' rolls for the monsters and maximum damage more often than not, while the poor players can seldom roll above a '5' on their d20s. What might otherwise have been an easy fight can easily turn into a debacle when you rely on your dice to carry the day.
How do you ensure victory before entering combat? Don't play fair. Stack the deck in your favour by taking every possible advantage of terrain and environment. By doing so the circumstances of battle are so far in your favour that they mitigate against the vagaries of random chance.
If you cannot stack the odds in your favour, in other words win before entering battle, then don't initiate an attack. Obviously there are going to be lots of occasions when you are forced to fight before you are ready, and in these circumstances, Sun Tzu advises that you fight defensively. If you have taken precautions to minimize your vulnerability then the advantage always goes to the defender.
15. Those skilled in war cultivate the Tao and preserve the laws and are therefore able to formulate victorious policies.
16. Now the elements of the art of war are first, measurement of space; second, estimation of quantities; third, calculations; fourth, comparisons; and fifth, chances of victory.
17. Measurements of space are derived from the ground.
18. Quantities derive from measurement, figures from quantities, comparisons from figures, and victory from comparison.
Measurement of space includes an assessment of the geographic area; estimation of quantities involves determining the numbers of the enemy, their equipment, and morale; comparison is made between your force and the enemy's, and calculations are made to determine whether or not you will defeat them. Only after considering these factors can you launch an attack with confidence.
19. Thus a victorious army is as a hundredweight balanced against a grain; a defeated army as a grain balanced against a hundredweight.
20. It is because of disposition that a victorious general is able to make his people fight with the effect of pent-up waters which, suddenly released, plunge into a bottomless abyss.
If you plan for every contingency and attack only when you are sure to win, you can be assured of the support of your henchmen and hirelings. Such will be their confidence in your plan that morale checks will be unnecessary and they are unlikely to flee at the worst possible moment. If you leave battles to chance, an unlucky turn of events can have your hirelings rolling, and probably failing, morale checks and leaving you in an even worse situation, thus compounding the unlucky dice dice rolls and making defeat all too likely.
Welcome Back to the Labyrinth
"We have been away far too long, my friends," Ashoka declared, his face lit by the eldritch green glow of his staff. "But we have finally returned to the labyrinth whence our adventures first began."
"Just imagine the treasures that lie within," said Yun Tai, flexing his mighty muscles. "Wealth enough to live in luxury the rest of our days."
"And arcane artifacts of great power," added Ashoka his words dripping with avarice. "All ours for the taking!"
"Umm...guys?" Nysa interrupted. "Do you hear something dripping?"