Sun Tzu begins his treatise by saying that "The art of war is of vital importance to the State. A matter of life and death, a road either to safety or to ruin."
Sun Tzu says that the art of war is governed by five factors. These are:
(1) The Moral Law - this causes people to be in complete accord with their ruler, so that they will follow him regardless of their lives.
(2) Heaven - stands for the seasonal conditions.
(3) Earth - stands for the physical terrain ("distances great and small, open ground and narrow passes.")
(4) The Commander - the virtues of the military commander.
(5) Method and discipline - the marshalling of the army and its divisions (logistics, expenditure)
Sun Tzu says that all warfare is based on deception.
The objective of war is victory. Sun Tzu says that if the campaign is long-drawn-out, the resources of the State will not be equal to the strain. Sun Tzu says that there is no instance of a country benefiting from prolonged warfare. Sun Tzu says that there is no merit in fighting and conquering. Merit consists in breaking the enemy's resistance without fighting. Sun Tzu quotes the proverb "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."
Sun Tzu says that "The fighters must first put themselves beyond the possibility of defeat, and then wait for an opportunity of defeating the enemy. To secure ourselves against defeat lies in our own hands, but the opportunity of defeating the enemy is provided by a mistake on the enemy's part." Security against defeat implies defensive tactics, and the ability to defeat the enemy means taking the offensive. Battles are won by committing no mistakes. Sun Tzu says that in war the strategist only seeks battle after the victory has been won, whereas the one destined to defeat first fights and looks for victory afterwards!
Sun Tzu says that in war the direct method may be used for commencing battle, but indirect methods will be needed in order to secure victory. There are only two methods of attack - the direct and the indirect - but in combination these give rise to an endless series of strategies.
Sun Tzu says that one can be sure of success if one only attacks places which are undefended (weak points). On the other hand, the safety of the defense can be ensured only if one holds positions that cannot be attacked (strong points). Sun Tzu says that if one knows the place and the time of the coming battle, one can marshal one's forces from afar.
Sun Tzu advices the general not to repeat the tactics (that have gained one victory) again and again. The way is to avoid what is strong and to strike at what is weak - like water, taking the line of least resistance.
Sun Tzu says that maneuvering with a disciplined army is advantageous, but with an undisciplined multitude most dangerous. An army without its supply-train, without provisions and without bases of supply is lost. Forming a single cohesive body, it is impossible either for the brave to advance alone, or for the cowardly to retreat alone. Sun Tzu says that it is a military axiom not to advance uphill against the enemy, nor to oppose him when he comes downhill.
Sun Tzu says that the art of war teaches us to rely not on the likelihood of the enemy's not coming, but rather on the fact that we have made our position unassailable. Sun Tzu says that five faults must be avoided: Recklessness, Cowardice, A hasty temper, A (false) sense of honor and Over concern for one's troops.
Sun Tzu says that if fighting is sure to result in victory, then the general must fight even though the ruler forbids it; if fighting will not result in victory, then the general must not fight even at the ruler's commands. The general must advance without coveting fame and retreat without fearing disgrace. Sun Tzu says that rapidity is the essence of war. And that the army must be kept continually on the move.
Sun Tzu says that a spirit of enterprise must be cultivated if one wants to succeed in the attack and win the battle. Otherwise, war is just a waste of time and will lead to a stalemate. Sun Tzu warns that the general should be fully prepared for war - because a kingdom that has been destroyed can never again come into being, and the dead can not be brought back to life.
For those interested in the study of war and war strategy, you can't do without this book...