You seem to be using destroy and open warfare synonymously. The Art of War is about one of these, not the other:

http://www.thefreedictionary.com/destroy

  de·stroy  (d-stroi)
  v. de·stroyed, de·stroy·ing, de·stroys
  v.tr.
  1. To ruin completely; spoil: The ancient manuscripts were destroyed by fire.
  2. To tear down or break up; demolish. See Synonyms at ruin.
  3. To do away with; put an end to: "In crowded populations, poverty destroys the possibility of cleanliness" (George Bernard Shaw).
  4. To kill: destroy a rabid dog.
  5. To subdue or defeat completely; crush: The rebel forces were destroyed in battle.

See 5.