"_In war everything is very simple, but the simplest thing is difficult_,"[26] runs his famous saying. Why is the simplest thing difficult? Because of the friction of war. And how can that friction be minimized? Only by force of character, and the military virtues of discipline, perseverance, resolution, energy, and boldness. Hence the great emphasis which he always and everywhere lays upon character and these military virtues as the deciding factors in war. "_Friction is the only conception which in a general way corresponds to that which distinguishes real war from war on paper_," he says. Each individual of the army "keeps up his own friction in all directions." "The danger which war brings with it, the bodily exertions which it requires, augment this evil so much that they may be regarded as the greatest causes of it."[27] "_This enormous friction is everywhere brought into contact with chance_, and thus facts take place upon which it was impossible to calculate, their chief origin being chance. As an instance of one such chance take the weather. Here the fog prevents the enemy from being discovered in time,--a battery from firing, or a report from reaching the general. The rain (mud) prevents a battalion from arriving,--or the cavalry from charging effectively, because it had stuck fast in the heavy ground." And so on. Consider for examples the foggy mornings of Jena or Austerlitz, of Eylau, the Katzbach, Grosbeeren, Dennewitz, Pultusk, Dresden, Sadowa; or the mud of Poland, the snow of Russia, or, latest, the mud of Manchuria. "_Activity in war is movement in a resistant medium._" "_The knowledge of friction is a chief part of that so often talked of experience in war_, which is required in a good general." "It is therefore this friction which makes that which appears easy in war so difficult in reality."[28] In considering any situation in war we must therefore always add to the known circumstances--friction. WAR ITSELF