Security against defeat implies defensive tactics; ability to defeat the enemy means taking the offensive.
 Sun Tzu, The Art of War (5th century BC). copy citation

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Author Sun Tzu
Source The Art of War
Topic tactic security
Date 5th century BC
Language English
Reference
Note Translated by Lionel Giles
Weblink http://www.gutenberg.org/files/17405/17405-h/17405-h.htm

Context

“To secure ourselves against defeat lies in our own hands, but the opportunity of defeating the enemy is provided by the enemy himself.
3. Thus the good fighter is able to secure himself against defeat, but cannot make certain of defeating the enemy.
4. Hence the saying: One may know how to conquer without being able to do it.
5. Security against defeat implies defensive tactics; ability to defeat the enemy means taking the offensive. 6. Standing on the defensive indicates insufficient strength; attacking, a superabundance of strength.
7. The general who is skilled in defense hides in the most secret recesses of the earth; he who is skilled in attack flashes forth from the topmost heights of heaven.” source