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.
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.
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.