Our faith in others betrays that we would rather have faith in ourselves. Our longing for a friend is our betrayer. And often with our love we want merely to overcome envy. And often we attack and make ourselves enemies, to conceal that we are vulnerable.
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.