But though these changed conditions must, of course, _modify_ Clausewitz's details in many important particulars, still (to complete our circle and leave off where we started) I repeat that, as human nature never changes, and as the moral is to the physical as three to one in war, Clausewitz, as the great realistic and practical philosopher on the actual nature of war, as _the chief exponent of the moral and spiritual forces in war_, will ever remain invaluable in the study of war.
Consider what unsurpassed opportunities he had for observing and reflecting on the influence of enthusiasm and passion, of resolution and boldness, of vacillation and weakness, of coolness and caution, of endurance and hardship, of patriotism and freedom, of ambition and of glory--on war, either by his own experience or by conversation with other equally experienced soldiers, during that long period of almost endless wars between 1793 and 1815.
The fervour and enthusiasm and boundless energy of the Revolution, which drove the French forward, smashing everything before them, at the beginning; the ambition, military glory, plunder and greed, which animated them later on; the patriotism, religious and loyal devotion, and stern endurance, which nerved the Russian hosts then as now; that awful Moscow winter campaign, when human nature rose to its highest and sank to its lowest, when the extremes of heroic endurance and selfish callousness were visible side by side; the magnificent uprising of the spirit of liberty and freedom from intolerable oppression in Germany, which gave to the Prussian recruits and Landwehr the same driving force that revolutionary enthusiasm had formerly given to the French; the passing, therefore, in 1813 of the moral superiority, the greater driving force, from the French to the allies. Clausewitz saw all this; he conversed intimately with such men as Scharnhorst and Gneisenau, who saw and guided it, too. All his friends had seen it also. No wonder, then, that such an unexampled series of warlike phenomena deeply impressed his reflective mind with the supreme importance of the moral and spiritual factors in war.
His opportunities for long-continued observation of warlike phenomena were far greater than those of any writer since his day, and it is to be hoped they will remain so. For we have no desire to see another series of wars such as the Napoleonic. It is fortunate for us that there was then such a man as Clausewitz to sum up for us so simply and so clearly the accumulated experiences of those long, long years of carnage and devastation.