As an aide-de-camp and friend of Gen. Pillow, he naturally sympathized with that officer in the unseemly dissensions which broke out between Gen. Scott on the one hand and Gens. Worth and Pillow and other distinguished officers on the other, and was more or less interested in the protracted military investigations which followed the war. In this way he made the military history of the war a careful study, and he studied not only carefully but intelligently. His military education, his actual service in the war, his taste for military studies, the position which he held on Pillow’s staff, and his very decided ability fitted him peculiarly to be the military historian of the war. In order to write his history he obtained a protracted leave of absence, and devoted himself faithfully to his work. That he was prejudiced against both Gen. Scott and Gen. Taylor, and criticizes both of these eminent soldiers too severely, and very unjustly, is true, but he tells the story of the campaign with singular fidelity and in a masterly way. He understood what was done and has told it in a style worthy of the great deeds which he narrates. His obstinate temper, his prejudice, and his contentious spirit are too often apparent, but we pardon them in reading his luminous account of the many intricate movements of the troops, and the wonderful battles which were fought in the Valley of Mexico. However unjust his criticisms, they are always able and dignified, and compel our respect. It is not strange that he did not appreciate the romantic performances of Kearney and Doniphan and Fremont, for he viewed all things as one fresh from the Military Academy, where are taught the duties of a soldier, not those of a statesman, and he was still a youth of 26 when he wrote his history. He could not understand the meaning of Kearney’s long march across the desert, of Doniphan’s wonderful expedition, or of Fremont’s daring exploits and strange adventures. He did not see that statesmen had duties more important than those of the soldier, and that Doniphan and Kearney and Fremont were adding an empire to the Union, while Scott and Taylor were covering our armies with undying glory and securing the possession of the conquests which our little armies were making in New Mexico and California. A soldier of distinction, (Stevens,) in reviewing the book, says: “The work is professedly critical, and much space is devoted to the discussion of the political and military movements of both Mexico and the United States. A very thorough exposition has been made of both campaigns and of battles. The style is decidedly good. His view of the origin of the war is eminently just and told in sufficient detail.” The freedom with which he, a mere subaltern, criticizes the conduct of such veterans as Scott and Taylor, both of them his superior officers, and one of them the President of the United States and Commander-in-Chief of the Army, is remarkable.