Clausewitz's emphasis on the need to wage war as rationally as possible must be viewed as a normative recommendation not as a description of reality. The qualities that Clausewitz admires in the military genius are above all self-confidence; trust in his experience and intuition, the ability even in the heat of battle to stick confidently to his original goal. Since war is not an exact science, Clausewitz is also careful to note exceptions when he makes an observation or recommendation. Therefore, the identification of such so-called flaws in 'On War' actually enhances one's understanding of war as a human and social phenomenon. In order to be assured of victory, the opponents will theoretically employ all available force against each other. This physical force of interaction is directly related to other principles developed later in 'On War' such as the maximum concentration of forces in space and time, and the importance of achieving numerical superiority in battle.