Vom kriege.

Vom Kriege is the basic work on the Western way of war. For Clauswitz, war is "politics by other means". It concentrates on defeating the enemy by massing overwhelming force at the enemy's weak point. In his rationalistic model, the prince (or other governing elite) begins with a set of objectives and chooses the most cost-effective way of accomplishing them. If force is seen as that way, then the prince chooses war. When the objectives have been achieved, then the war has been won regardless of conditions and dispositions on the field.

Clausewitz is read by every officer cadet in every decent military academy in the world. Written in the 18th century, Vom Kriege is as relevant today as the day it was published.