Hostile armies may face each other for years, striving for the victory which is decided in a single day. This being so, to remain in ignorance of the enemy's condition simply because one grudges the outlay of a hundred ounces of silver in honors and emoluments, is the height of inhumanity.
Sun TzuWith regard to narrow passes, if you can occupy them first, let them be strongly garrisoned and await the advent of the enemy.
Sun Tzu