The work to which these lines serve as a preface occupied almost entirely the last twelve years of the life of my inexpressibly beloved husband, who has unfortunately been torn too soon from myself and his country. To complete it was his most earnest desire; but it was not his intention that it should be published during his life; and if I tried to persuade him to alter that intention, he often answered, half in jest, but also, perhaps, half in a foreboding of early death: “_Thou_ shalt publish it.” These words (which in those happy days often drew tears from me, little as I was inclined to attach a serious meaning to them) make it now, in the opinion of my friends, a duty incumbent on me to introduce the posthumous works of my beloved husband, with a few prefatory lines from myself; and although here may be a difference of opinion on this point, still I am sure there will be no mistake as to the feeling which has prompted me to overcome the timidity which makes any such appearance, even in a subordinate part, so difficult for a woman. It will be understood, as a matter of course, that I cannot have the most remote intention of considering myself as the real editress of a work which is far above the scope of my capacity: I only stand at its side as an affectionate companion on its entrance into the world. This position I may well claim, as a similar one was allowed me during its formation and progress. Those who are acquainted with our happy married life, and know how we shared _everything_ with each other—not only joy and sorrow, but also every occupation, every interest of daily life—will understand that my beloved husband could not be occupied on a work of this kind without its being known to me. Therefore, no one can like me bear testimony to the zeal, to the love with which he laboured on it, to the hopes which he bound up with it, as well as the manner and time of its elaboration. His richly gifted mind had from his early youth longed for light and truth, and, varied as were his talents, still he had chiefly directed his reflections to the science of war, to which the duties of his profession called him, and which are of such importance for the benefit of States. Scharnhorst was the first to lead him into the right road, and his subsequent appointment in 1810 as Instructor at the General War School, as well as the honour conferred on him at the same time of giving military instruction to H.R.H. the Crown Prince, tended further to give his investigations and studies that direction, and to lead him to put down in writing whatever conclusions he arrived at. A paper with which he finished the instruction of H.R.H. the Crown Prince contains the germ of his subsequent works. But it was in the year 1816, at Coblentz, that he first devoted himself again to scientific labours, and to collecting the fruits which his rich experience in those four eventful years had brought to maturity. He wrote down his views, in the first place, in