To be practical, any plan must take account of the enemy's power to frustrate it.
Carl von ClausewitzRather than comparing [war] to art we could more accurately compare it to commerce, which is also a conflict of human interests and activities; and it is still closer to politics, which in turn may be considered as a kind of commerce on a larger scale.
Carl von ClausewitzWar is not merely a political act but a real political instrument, a continuation of political intercourse, a carrying out of the same by other means.
Carl von Clausewitz