Knowledge of the enemy's dispositions can only be obtained from other men.
Until death itself comes, no calamity need be feared
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.
If your enemy is superior, evade him
He will win who has military capacity and is not interfered with by the sovereign.
All warfare is based on deception. There is no place where espionage is not used. Offer the enemy bait to lure him.