To be practical, any plan must take account of the enemy's power to frustrate it.
Carl von ClausewitzWhenever armed forces . . . are used, the idea of combat must be present. . . . The end for which a soldier is recruited, clothed, armed, and trained, the whole object of his sleeping, eating, drinking, and marching is simply that he should fight at the right place and the right time.
Carl von ClausewitzThe object of defense is preservation; and since it is easier to hold ground than to take it, defense is easier than attack. But defense has a passive purpose: preservation; and attack a positive one: conquest.... If defense is the stronger form of war, yet has a negative object, it follows that it should be used only so long as weakness compels, and be abandoned as soon as we are strong enough to pursue a positive object.
Carl von Clausewitz