Some might suggest that only a military man could properly write this work. But, in the first place, the author did not wish to prepare a technical military account of the war. His aim was to offer a correct and complete view of it suitable for all interested in American history, and it will be found that politics, diplomacy and other phases of the subject required as full investigation as did its military aspects. Secondly, the author took pains to qualify himself for his task. The real difficulty of the commanding general consists in applying the principles of war under complicated, obscure and changeful conditions, and in overcoming "friction" of many sorts. The intellectual side of the art is readily enough understood. "In war everything is very simple," wrote Clausewitz, the fountainhead of the modern system. "The theory of the great speculative combinations of war is simple enough in itself," said Jomini; "it only requires intelligence and attentive reflection." "Strategy is the application of common sense to the conduct of war," declared Von Moltke. Arnold in his Lectures on Modern History said: "An unprofessional person may, without blame, speak or write on military subjects, and may judge of them sufficiently;" and the eminent military authority, G. F. R. Henderson, endorsed this view. "The theory of war is simple," wrote another expert, "and there is no reason why any man who chooses to take the trouble to read and reflect carefully on one or two of the acknowledged best books thereon, should not attain to a fair knowledge thereof." As may be seen from the list of printed sources, the present author--beginning with the volumes recommended by a board of officers to the graduates of the United States Military Academy--did much more than is here proposed. Finally, during the entire time occupied in writing this work he fortunately enjoyed the advantage of corresponding and occasionally conferring with Brigadier General Oliver L. Spaulding, Jr., of the United States Field Artillery, formerly instructor at the Army Service Schools, Fort Leavenworth, and more recently Assistant Commandant of the School of Fire, Fort Sill, who had distinguished himself not only in the service but as a writer on professional subjects. General Spaulding has kindly discussed with the author such military questions as have arisen, and has read critically all the battle chapters. No responsibility should, however, be attached to him, if a mistake is detected.[P.4]