Defense refers to defending some thing or someone. If you speak up in defense then you are speaking in order to defend something. Every government is responsible for the defense of their borders and their citizens, and this can be managed in a wide variety of ways. The defense of the helpless and innocent is one of the basic principles of chivalry.
If our air forces are never used, they have achieved their finest goal
Self-defense is the clearest of all laws, and for this reason lawyers didn't make it