Carl von Clausewitz

Knowledge in war is very simple, being concerned with so few subjects, and only with their final results at that. But this does not make its application easy.

... in the whole range of human activities, war most closely resembles a game of cards.

Timidity is the root of prudence in the majority of men.

A prince or general can best demonstrate his genius by managing a campaign exactly to suit his objectives and his resources, doing neither too much nor too little.

If a segment of one's force is located where it is not sufficiently busy with the enemy, or if the troops are on the march - that is, idle - while the enemy is fighting, then these forces are being managed uneconomically. In this sense they are being wasted, which is even worse than using them inappropriately.