These are the six ways of courting defeat - neglect to estimate the enemy's strength; want of authority; defective training; unjustifiable anger; nonobservance of discipline; failure to use picked men.
He who knows things, and in fighting puts his knowledge into practice, will win his battles. He who knows them not, nor practices them, will surely be defeated.
Those who are victorious plan effectively and change decisively. They are like a great river that maintains its course but adjusts its flow...they have form but are formless. They are skilled in both planning and adapting and need not fear the result of a thousand battles: for they win in advance, defeating those that have already lost.
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.
Those who do not know the plans of competitors cannot prepare alliances. Those who do not know the lay of the land cannot maneuver their forces. Those who do not use local guides cannot take advantage of the ground.
It is imperative to contest all factions for complete victory, so the army is not garrisoned and the profit can be total. This is the law of strategic siege.
If your enemy is secure at all points, be prepared for him. If he is in superior strength, evade him. If your opponent is tempermental, 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. If sovereign and subject are in accord, put division between them. Attack him where he is unprepared, appear where you are not expected.