Sun Tzu said:

The art of war is of vital importance to the state. It is a matter of life and death, a road either to safety or to ruin. Hence under no circumstances can it be neglected.

The art of war is governed by five constant factors, all of which need to be taken into account. They are: the Moral Law; Heaven; Earth; the Commander; Method and discipline.

The Moral Law causes the people to be in complete accord with their ruler, so that they will follow him regardless of their lives, undismayed by any danger.

Heaven signifies night and day, cold and heat, times and seasons.

Earth comprises distances, great and small; danger and security; open ground and narrow passes; the chances of life and death.

The Commander stands for the virtues of wisdom, sincerity, benevolence, courage, and strictness.

By Method and discipline are to be understood the marshaling of the army in its proper subdivisions, the gradations of rank among the officers, the maintenance of roads by which supplies may reach the army, and the control of military expenditure.

These five factors should be familiar to every general. He who knows them will be victorious; he who knows them not will fail.

Therefore, when seeking to determine your military conditions, make your decisions on the basis of a comparison in this wise:

Which of the two sovereigns is imbued with the Moral Law?

Which of the two generals has the most ability?

With whom lie the advantages derived from Heaven and Earth?

On which side is discipline most rigorously enforced?
Tu Mu alludes to the remarkable story of Ts'ao Ts'ao (A.D. I55 - 220), who was such a strict disciplinarian that once, in accordance with his own severe regulations against injury to standing crops, he condemned himself to death for having allowed his horse to stray into a field of corn! However, in lieu of losing his head, he was persuaded to satisfy his sense of justice by cutting off his hair. "When you lay down a law, see that it is not disobeyed; if it is disobeyed, the offender must be put to death."
Which army is the stronger?

On which side are officers and men more highly trained?

In which army is there the most absolute certainty that merit will be properly rewarded and misdeeds summarily punished?

By means of these seven considerations I can forecast victory or defeat. The general who hearkens to my counsel and acts upon it will conquer--let such a one be retained in command! The general who hearkens not to my counsel nor acts upon it will suffer defeat--let such a one be dismissed! But remember: While heeding the profit of my counsel, avail yourself also of any helpful circumstances over and beyond the ordinary rules and modify your plans accordingly.

All warfare is based on deception. Hence, when able to attack, we must seem unable; when using our forces, we must seem inactive; when we are near, we must make the enemy believe we are far away; when far away, we must make him believe we are near. Hold out baits to entice the enemy. Feign disorder, and crush him. If he is secure at all points, be prepared for him. If he is in superior strength, evade him. If your opponent is of choleric temper, seek to irritate him. Pretend to be weak, that he may grow arrogant. If he is taking his ease, give him no rest. If his forces are united, separate them. Attack him where he is unprepared, appear where you are not expected.

The general who wins a battle makes many calculations in his temple before the battle is fought. The general who loses a battle makes but few calculations beforehand. Thus do many calculations lead to victory, and few calculations to defeat; how much more no calculation at all! It is by attention to this point that I can foresee who is likely to win or lose.

II: ON WAGING WAR

In the operations of war, where there are in the field a thousand swift chariots, ten thousand heavy chariots, and a hundred thousand mail-clad soldiers, with provisions enough to carry them a thousand li*, the expenditure at home and at the front, including entertainment of guests, small items such as glue and paint, and sums spent on chariots and armor, will reach the total of a thousand ounces of silver per day. Such is the cost of raising an army of a hundred thousand men.

When you engage in actual fighting, if victory is long in coming, the men's weapons will grow dull and their ardor will be dampened. If you lay siege to a town, you will exhaust your strength, and if the campaign is protracted, the resources of the state will not be equal to the strain. Never forget: When your weapons are dulled, your ardor dampened, your strength exhausted, and your treasure spent, other chieftains will spring up to take advantage of your extremity. Then no man, however wise, will be able to avert the consequences that must ensue.

Thus, though we have heard of stupid haste in war, cleverness has never been seen associated with long delays. In all history, there is no instance of a country having benefited from prolonged warfare. Only one who knows the disastrous effects of a long war can realize the supreme importance of rapidity in bringing it to a close. It is only one who is thoroughly acquainted with the evils of war who can thoroughly understand the profitable way of carrying it on.

The skillful general does not raise a second levy, neither are his supply wagons loaded more than twice. Once war is declared, he will not waste precious time in waiting for reinforcements, nor will he turn his army back for fresh supplies, but crosses the enemy's frontier without delay. The value of time--that is, being a little ahead of your opponent--has counted for more than either numerical superiority or the nicest calculations with regard to commissariat.

Bring war material with you from home, but forage on the enemy. Thus the army will have food enough for its needs. Poverty of the state exchequer causes an army to be maintained by contributions from a distance. Contributing to maintain an army at a distance causes the people to be impoverished.

On the other hand, the proximity of an army causes prices to go up; and high prices cause people's substance to be drained away. When their substance is drained away, they will be afflicted by heavy exactions. With this loss of substance and exhaustion of strength, the homes of the people will be stripped bare, and their incomes dissipated; at the same time government expenses for broken chariots, worn-out horses, breastplates and helmets, bows and arrows, spears and shields, protective mantlets, draught oxen and heavy wagons, will amount to almost half its total revenue.

A wise general makes a point of foraging on the enemy. One cartload of the enemy's provisions is equivalent to twenty of one's own, and likewise a single picul** of his provender is equivalent to twenty from one's own store.

Now, in order to kill the enemy, our men must be roused to anger. For them to perceive the advantage of defeating the enemy, they must also have their rewards. Thus, when you capture spoils from the enemy, they must be used as rewards, so that all your men may have a keen desire to fight, each on his own account.

Therefore in chariot fighting, when ten or more chariots have been taken, those should be rewarded who took the first. Our own flags should be substituted for those of the enemy, and the chariots mingled and used in conjunction with ours. The captured soldiers should be kindly treated and kept. This is called using the conquered foe to augment one's own strength.

In war, then, let your great object be victory, not lengthy campaigns. Thus it may be known that the leader of armies is the arbiter of the people's fate, the man on whom it depends whether the nation shall be in peace or in peril.

* 2.78 modern li make a mile. The length may have varied slightly since Sun Tzu's time.

** A Chinese unit of weight equal to 133.33 pounds.

III: THE SHEATHED SWORD

To fight and conquer in all your battles is not supreme excellence; supreme excellence consists in breaking the enemy's resistance without fighting. In the practical art of war, the best thing of all is to take the enemy's country whole and intact; to shatter and destroy it is not so good. So, too, it is better to capture an army entire than to destroy it, to capture a regiment, a detachment, or a company entire than to destroy them.

Thus the highest form of generalship is to balk the enemy's plans; the next best is to prevent the junction of the enemy's forces; the next in order is to attack the enemy's army in the field; and the worst policy of all is to besiege walled cities, because the preparation of mantlets, movable shelters, and various implements of war will take up three whole months; and the piling up of mounds over against the walls will take three months more. The general, unable to control his irritation, will launch his men to the assault like swarming ants, with the result that one third of his men are slain, while the town still remains untaken. Such are the disastrous effects of a siege.

The skillful leader subdues the enemy's troops without any fighting; he captures their cities without laying siege to them; he overthrows their kingdom without lengthy operations in the field. With his forces intact he disputes the mastery of the empire, and thus, without losing a man, his triumph is complete.

This is the method of attacking by stratagem of using the sheathed sword.

It is the rule in war: If our forces are ten to the enemy's one, to surround him; if five to one, to attack him; if twice as numerous, to divide our army into two, one to meet the enemy in front, and one to fall upon his rear; if he replies to the frontal attack, he may be crushed from behind; if to the rearward attack, he may be crushed in front.

If equally matched, we can offer battle; if slightly inferior in numbers, we can avoid the enemy; if quite unequal in every way, we can flee from him. Though an obstinate fight may be made by a small force, in the end it must be captured by the larger force.

The general is the bulwark of the state: if the bulwark is strong at all points, the state will be strong; if the bulwark is defective, the state will be weak.

There are three ways in which a sovereign can bring misfortune upon his army:

By commanding the army to advance or to retreat, being ignorant of the fact that it cannot obey. This is called hobbling the army.

By attempting to govern an army in the same way as he administers a kingdom, being ignorant of the conditions that obtain in an army.

This causes restlessness in the soldiers' minds. Humanity and justice are the principles on which to govern a state, but not an army; opportunism and flexibility, on the other hand, are military rather than civic virtues.

By employing the officers of his army without discrimination, through ignorance of the military principle of adaptation to circumstances. This shakes the confidence of the soldiers.
Su-ma Ch'ien about 100 B.C. added to this section: If a general is ignorant of the principle of adaptability, he must not be entrusted with a position of authority. The skillful employer of men will employ the wise man, the brave man, the covetous man, and the stupid man. For the wise man delights in establishing his merit, the brave man likes to show his courage in action, the covetous man is quick at seizing advantages, and the stupid man has no fear of death.
When the army is restless and distrustful, trouble is sure to come from the other feudal princes. This is simply bringing anarchy into the army, and flinging victory away. Thus we may know that there are five essentials for victory:

He will win who knows when to fight and when not to fight.

He will win who knows how to handle both superior and inferior forces.

He will win whose army is animated by the same spirit throughout all its ranks.

He will win who, prepared himself, waits to take the enemy unprepared.

He will win who has military capacity and is not interfered with by the sovereign.

If you know the enemy and know yourself, you need not fear the result of a hundred battles. If you know yourself but not the enemy, for every victory gained you will also suffer a defeat. If you know neither the enemy nor yourself, you will succumb in every battle.