[The Spartans] should not make war often, or long, with the same enemy, lest that they should train and instruct them in war, by habituating them to defend themselves.

never disperse your focus unless absolutely necessary. Face one adversary at a time.

it is bad to repeat the same thing several times when fighting the enemy.

Know your enemy and know yourself and you can fight a hundred battles without disaster

You must achieve the spirit of not allowing the enemy to attack a second time.

If you have an enemy, then learn and know your enemy, don't just be mad at him or her

You can only fight the way you practice

Face a single foe as if you are facing ten thousand enemies; face ten thousand enemies as a single foe

You may have to fight a battle more than once to win it.

It pays to know the enemy - not least because at some time you may have the opportunity to turn him into a friend.

The art of war is simple enough. Find out where your enemy is. Get at him as soon as you can. Strike him as hard as you can, and keep moving on.

(1) He will win who knows when to fight and when not to fight. (2) He will win who knows how to handle both superior and inferior forces. (3) He will win whose army is animated by the same spirit throughout all its ranks. (4) He will win who, prepared himself, waits to take the enemy unprepared. (5) He will win who has military capacity and is not interfered with by the sovereign. 18. Hence the saying: If you know the enemy and know yourself, you need not fear the result of a hundred battles. If you know yourself but not the enemy, for every victory gained you will also suffer a defeat. If you know neither the enemy nor yourself, you will succumb in every battle.

The art of war teaches us to rely not on the likelihood of the enemy's not coming, but on our own readiness to receive him; not on the chance of his not attacking, but rather on the fact that we have made our position unassailable.

You will only injure yourself if you take notice of despicable enemies.