War, The Art of War (孫子)

兵者，詭道也。故能而示之不能，用而示之不用，近而示之遠，遠而示之近。

- 孫子

All warfare is based on deception. Hence, when we are able to attack, we must seem unable; when using our forces, we must appear inactive; when we are near, we must make the enemy believe we are far away; when far away, we must make him believe we are near.

- Sun Tzu, The Art of War

Common examples can also be found in English use, such as verse 18 in Chapter 1. This has been abbreviated to its most basic form and condensed into the English modern proverb:

All warfare is based on deception.

http://en.wikipedia.org/wiki/The_Art_of_War

War, The Art of War

故曰：知彼知己，百戰不殆；不知彼而知己，一勝一負；不知彼，不知己，每戰必殆。

- 孫武, 孫子, 謀攻篇 第三

So it is said that if you know your enemies and know yourself, you can win a hundred battles without a single loss. If you only know yourself, but not your opponent, you may win or may lose. If you know neither yourself nor your enemy, you will always endanger yourself.

- Sun Tzu, The Art of War

Verses from the book occur in modern daily Chinese idioms and phrases, such as the last verse of Chapter 3.

http://en.wikipedia.org/wiki/The_Art_of_War

War, Sun-Tzu

知彼知己百戰不殆。

- 孫子

If you know the enemy and know yourself, you need not fear the result of a hundred battles.

- Sun-Tzu (孫子)