In these days of large armies and intense military enthusiasm, the very title of a military book commends it, prima facie, to public interest; and when it promises to elucidate and systematize the intricate subject of military law, it has great specific importance in the eyes of the tens of thousands of officers who are constantly called upon to administer that law, and to whom the duties of courts-martial are new and difficult.  But, to understand still more clearly the great value of such a work, supposing it to be well written, we must go back in the history of military courts, and see how little had been done to render them systematic and uniform,—­what a comparatively unoccupied field the author had to reap in,—­what needs there were to supply; and then we shall be better able to criticize his work, and to judge of its practical value.

For a very long period we followed, in our army, the practice of the English courts-martial, as we adopted the English Common Law in our civic courts.

The military code to be applied and administered by courts-martial is contained in the Act of Congress of the 10th of April, 1806, commonly called “The Rules and Articles of War,” and in a few other acts and parts of acts, supplementary to these, which have been enacted from time to time, as circumstances seemed to require.

In the year 1839, Major-General Macomb, commander-in-chief of the army, prepared a little treatise on “The Practice of Courts-Martial,” which, in lieu of something better, was generally used; and the modes of proceeding and forms of orders and records there given established uniformity in the actions and duties of such courts throughout the army.

Five or six years later, Captain John P. O’Brien, of the Fourth Artillery, issued “A Treatise on American Military Law and Practice of Courts-Martial.”  This work evinced a great deal of legal research, and a thorough knowledge of the practical applications of military law; but it is voluminous, wanting in arrangement, and, while valuable as a storehouse from which to draw materials, not suited for ready reference, or for the study of beginners.  It is now, we believe, out of print; and, as its accomplished author is not living, it can hardly be adapted to the wants of the army at the present day.

In the year 1846, Captain William C. De Hart, of the Second Artillery, published his excellent work, entitled, “Observations on Military Law, and the Constitution and Practice of Courts-Martial.”  In his Preface he says,—­“Since the legal establishment of the army and navy of the United States, there has been no work produced, written for the express purpose,... and intended as a guide for the administration of military justice.”  And, in a note, he adds, “The small treatise on courts-martial by the late Major-General Macomb is no exception to the remark.”  He makes, if we remember rightly, no reference to Captain O’Brien’s work, which appeared but a short time before his own.