Wars, therefore, are to be undertaken for this end, that we may live in peace, without being injured; but when we obtain the victory, we must preserve those enemies who behaved without cruelty or inhumanity during the war.
It is one of the great troubles of life that we cannot have any unmixed emotions. There is always something in our enemy that we like, and something in our sweetheart that we dislike.
Therefore, to estimate the enemy situation and to calculate distances and the degree of difficulty of the terrain so as to control victory are virtues of the superior general.
So the principles of warfare are: Do not depend on the enemy not coming, but depend on our readiness against him. Do not depend on the enemy not attacking, but depend on our position that cannot be attacked.
There is no great harm in the theorist who makes up a new theory to fit a new event. But the theorist who starts with a false theory and then sees everything as making it come true is the most dangerous enemy of human reason.
To demand of strength that it should not express itself as strength, that it should not be a desire to overcome, a desire to throw down, a desire to become master, a thirst for enemies and resistances and triumphs, is just as absurd as to demand of weakness that it should express itself as strength.