The 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 ClausewitzAs each man's strength gives out, as it no longer responds to his will, the inertia of the whole gradually comes to rest on the commander's will alone. The ardor of his spirit must rekindle the flame of purpose in all others; his inward fire must revive their hope.
Carl von Clausewitz