Invincibility is in oneself, and vulnerability is in the opponent. Invincibility is a matter of defense, vulnerability is a matter of attack. Therefore skillful warriors are able to be invincible, but they cannot cause opponents to be vulnerable. That is why it is said that victory is discerned and not manufactured.
Thus we may know that there are five essentials for victory: He will win who knows when to fight and when not to fight. He will win who knows how to handle both superior and inferior forces. He will win whose army is animated by the same spirit throughout all its ranks. He will win who, prepared himself, waits to take the enemy unprepared. He will win who has military capacity and is not interfered with by the sovereign.
There are five dangerous faults which may affect a general: recklessness, which leads to destruction; cowardice, which leads to capture; a hasty temper, which can be provoked by insults; a delicacy of honour, which is sensitive to shame; over-solicitude for his men, which exposes him to worry and trouble.
Do not engage an enemy more powerful than you. And if it is unavoidable and you do have to engage, then make sure you engage it on your terms, not on your enemy's terms.
With regard to ground of this nature, be before the enemy in occupying the raised and sunny spots, and carefully guard your line of supplies. Then you will be able to fight with advantage.
Military tactics are like unto water; for water in its natural course runs away from high places and hastens downwards... Water shapes its course according to the nature of the ground over which it flows; the soldier works out his victory in relation to the foe whom he is facing. Therefore, just as water retains no constant shape, so in warfare there are no constant conditions. He who can modify his tactics in relation to his opponent and thereby succeed in winning, may be called a heaven-born captain.