When a general, unable to estimate the enemy's strength, allows an inferior force to engage a larger one, or hurls a weak detachment against a powerful one, and neglects to place picked soldiers in the front rank, the result must be rout.
Hence the saying: If you know the enemy and you know yourself, your victory will not stand in doubt; if you now Heaven and you know Earth, you may make your victory complete.
If we know that the enemy is open to attack, but are unaware that our own men are not in a condition to attack, we have gone only halfway towards victory.
The general who wins the battle makes many calculations in his temple before the battle is fought. The general who loses makes but few calculations beforehand.
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.
The ultimate in disposing one's troops is to be without ascertainable shape. Then the most penetrating spies cannot pry in nor can the wise lay plans against you.