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Bill Thayer

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 [decorative delimiter] Class of 1824

Vol. I

(Born N. Y.)

Dennis H. Mahan

(Ap'd Va.)


Military History. — Cadet at the Military Academy, Sep. 1, 1820, to July 1, 1824, when he was graduated and promoted in the Army to

Bvt. Second Lieut., Corps of Engineers, July 1, 1824.

Second Lieut., Corps of Engineers, July 1, 1824, to Jan. 1, 1832.

Served: at the Military Academy, 1824‑26, as Asst. Professor of Mathematics, Aug. 29, 1824, to Aug. 31, 1825, — and as Principal Asst. Professor of Engineering, Aug. 31, 1825, to Aug. 1, 1826; in Europe, on professional duty, by order of the War Department, Aug. 1, 1826, to June 15, 1830, being attached, by authority of the French Minister of War, as pupil to the Military School of Engineers and Artillerists at Metz, France, Jan. 1, 1929, to Mar. 10, 1830; and at the Military Academy, as Acting Professor of Engineering, Sep. 1, 1830, to Jan. 1, 1832, — and as

(Professor of Engineering, U. S. Military Academy, Jan. 1, 1832)

Professor of Engineering, Jan. 1, 1832, to Sep. 16, 1871.

Civil History. — Appointed, June 17, 1850, by the Governor of Virginia, Member of a Board of Engineers to decide the controversy between the City of Wheeling and the Baltimore and Ohio Railroad Company as to the true and proper route of the railroad to the city of Wheeling. Author of a "Treatise on Field Fortifications," 1836; of "Elementary Course of Civil Engineering," for the use of the Cadets of the U. S. Military Academy, 1837; of "Elementary Treatise on Advanced Guard, Outpost, Detachment Service of Troops, and Strategy." 1847‑64; "Elementary Treatise on Industrial Drawing," 1853; Additions to "Moseley's Mechanical Principles of Engineering and Architecture," of which he edited an American Edition, 1856; "Treatise on Fortification Drawing and Stereotomy," 1865; and "Elements of Permanent Fortification," 1867. Member of the Geographical Society of Paris, 1828; and of many scientific associations in the United States. Corporator of the National Academy of Sciences, Mar. 3, 1863, to Sep. 16, 1871. Degree of A. M. conferred by Brown University, R. I., — and by Princeton College, N. J., 1837; and of LL. D., by William and Mary College, Va., 1852, — by Brown University, R. I., 1852, — and by Dartmouth College, N. H., 1867.

Drowned in the Hudson River, near Stony Point, N. Y., Sep. 16, 1871: Aged 69.

Buried, West Point Cemetery, West Point, NY.

Biographical Sketch.

Professor Dennis Hart Mahan, whose distressful death, in his seventieth year, took place by drowning in the Hudson River, near Stony  p320 Point, Sep. 16, 1871, was born Apr. 2, 1802, in the city of New York. While yet an infant he was taken to Norfolk, Va., where he passed most of his boyhood. Destined for the profession of medicine, while studying with Dr. Archer in Richmond, Va., he learned by accident that drawing, for which he had a decided talent, was taught at West Point. Incited by a desire to acquire a knowledge of the graphic art, he, at the age of eighteen, secured a Cadet's appointment at the Military Academy through his influential and appreciative patron, the Hon. Thomas Newton, long the venerated Nestor of the U. S. House of Representatives. From his entrance into the Academy, his native talent, strong character, and persevering industry marked him as the foremost youth of his class. After the first year of his Cadetship he received, while only a third-classman, the unusual honor of being appointed an Acting Assistant Professor of Mathematics, which imposed upon him double duty, and often robbed him of his time for rest. Rarely did he get over six hours for sleep, but by this steady application he laid the sure foundation of his future eminence.

On July 1, 1824, he was graduated at the head of his class and promoted into the Corps of Engineers of the Army, in which he continued a Second Lieutenant till Jan. 1, 1832. After wish' service at the Academy as Assistant Professor of Mathematics till Aug. 3, 1825, and then as Principal Asst. Professor of Engineering till Aug. 1, 1826, he, by order of the War Department, was sent to Europe on professional duty, where he remained four years examining public works and military institutions, being attached from Jan. 1, 1829, to Mar. 10, 1830, by authority of the French Minister of War, as a pupil in the celebrated Military School of Application for Engineers and Artillerists at Metz, where distinguished officers like Poncelet were his professors, and many since known to fame were his fellow-students.

At Metz, a magnificent city even in the times of the Roman Emperors, and the grandest bulwark of France, fearlessly bidding defiance to every foe from Charles V till wrenched from Gallic sway by the greater hosts of another Charles of Germany, Mahan was the daily observer of its imposing architecture, its immense library rich in the works and manuscripts of the great masters of the art of war, its vast arsenal of trophies and arms, and its wondrous lines of fortification created by the genius of Vauban and Cormontaigne. Continually surrounded with such sites, breathing the air of the birthplace of so many whose swords and pens have rendered their names celebrated in military annals, on the very theatre where nations had so often contended for empire, instructed by teachers who had been educated in the campaigns of the great Napoleon, and constantly contending for the prize of engineering fame with the most brilliant pupils of a renowned school, it is not surprising that Mahan returned to his Alma Mater full of the lore and professional esprit fitted to make him worthy of the responsible trust to which he was at once called.

On Sep. 1, 1832, he took charge of the Department of Civil and Military Engineering at West Point, and continued at its head till removed by death, a period of over forty-one years. Though able men like Professors Crozet and Douglass had preceded him, such were the advancing requirements of the engineering art that it may be said Mahan had to almost recreate his entire course of instruction. As suitable textbooks did not exist, he, with great industry and research, at once endeavored to supply their place by lectures and lithographic notes. These became the groundwork of his subsequent publications on engineering and the art of war, which are of such priceless profit to our own Military Academy, are the adopted authorities for other schools in our country, and have even extended their influence to foreign lands.

 p321  These text-books, which were the life-long labor of this accomplished scholar, profound thinker, and most diligent student, and which have performed such an important part in the education of nearly our entire Army then living, and of many eminent engineers, can only briefly be commented upon in this limited space. To do full justice to their varied merits would require a very extended review.

Mahan's "Treatise on Field Fortification" made its first appearance in 1836, having since passed through six or seven editions, — in all over 10,000 copies. In 1865 it was greatly enlarged and improved, and now, with Military Mining and Siege Operations, constitutes Part I of "an Elementary Course of Military Engineering." This small volume contains in a very condensed and well-digested form a vast amount of valuable military information. It is unquestionably the best work on the subject in our language, has been fairly tested in our late civil war by both regular and volunteer officers, with many of whom it was a constant manual, and has received the highest commendations of experienced engineers at home and abroad.

Mahan's "Permanent Fortifications" constitutes Part II of the same "Elementary Course of Military Engineering." This work, which had to be adapted to the limited time allowed for the study of this branch of engineering at the Military Academy, is necessarily very concise, and touches only the general principles of permanent defenses, embra­cing a brief sketch of their component elements; an outline description and analysis of the various bastioned, tenailled, polygonal, and recent German systems; the influence of irregularities of sites on the character of works; the accessory means of defense; the defensive organization of frontiers; and the progress and changes of fortification from the earliest period to the present times. This admirably arranged work is a clear embodiment of the elements of the fortification art, and was the result of years of close study and unwearied research.

Mahan's "Advanced Guard, Outpost, and Detachment Service of Troops," published in 1847, was so enlarged in 1862 that it may now be more properly called an "Elementary Treatise on the Art of War." The demand for this work, amounting to over 8,000 copies, has been very great, it having been adopted in many State military schools, by the National Guard of New York, and by most volunteer and regular officers during the late Rebellion. Both this and the work on field fortifications were considered so indispensable in the Seceding States that they were re printed, the publisher having patriotically refused to sell them any copies.

Mahan's "Treatise on Fortification Drawing and Stereotomy," published in 1865, is an application of descriptive geometry to many problems of military constructions and stone-cutting, which subject had been taught orally for many years by the Professor to the Cadets of the Military Academy.

Mahan's "Course of Civil Engineering," first published in 1837, was continually enlarged and improved with the progress of engineering, till 1868, when he recast and rewrote the greater portion of the book. He was diligently employed till within a month of his death in entirely remodelling the work for a new edition, to meet the advancing requirements of engineering constructions. The value and immense popularity of this volume are best attested by its sale of over 15,000 copies. It is to be found in the hands of all our civil engineers, is the adopted text-book on engineering in many of our academies and colleges, has been reproduced in quarto form in England, being used in one of the government schools in India, and has been translated in whole or in part into several foreign languages. Nowhere in the same space can a like amount  p322 of engineering information be found as in this tersely written, compact work.

Mahan's American edition of "Moseley's Mechanical Principles of Engineering and Architecture," first published in 1856, reached a second edition in 1869. The clearness and elegance of Moseley's methods of treating the subjects of his work had already established its authority with the profession when Mahan undertook its revision, the correction of its many mathematical errors, and the addition of an invaluable appendix, thereby making the American edition an established classic of the mechanics of engineering and architecture.

Mahan's "Industrial Drawing," first published in 1853, has since gone through numerous editions. It was specially designed for academies and common schools, where it is now extensively used for teaching such as had no time to acquire a complete scientific education, but, as mechanics, would be in constant need of the elements of the geometrical and sometimes even of topographical drawing to render their ideas clear and intelligible to others. The practical mind of Mahan was drawn to the importance of the kind of knowledge by his frequent intercourse with the workmen of the West Point foundry, to whom he gave a gratuitous course of instruction on the subject, which was productive of the most excellent results.

Though best known as an author of works on engineering and the art of war, Mahan was a littérateur of no common order. His pen was ever in its rest ready to do vigorous battle for the advancement of truth, whether in professional matters, scientific subjects, or the current topics of the day; but his favorite themes were the Military Academy, the Army, and his Country.

Connected as Mahan had been for half a century with the Military Academy, for over forty years at the head of one of its most prominent departments of instruction, and dean of it S Faculty, no one had been more identified with the high mission and fair fame of this noble institution; and hence did he feel it particularly incumbent on him to brush away with his power­ful pen the slightest blot attempted to be placed upon its bright escutcheon, to fearlessly assert its priceless worth to the nation, and to promptly repel the insidious assaults of designing demagogues working its injury or downfall.

As the senior graduate who had not been retired, and the educator of all then in active service, Mahan naturally felt that the Army was in no small measure his own creation, and he was the foster-father of a numerous progeny of which he was justly proud; hence he was quick to shield worthy officers from unmerited reproach, or sound the praises of such men as Indicates a West Point graduate and gives his Class.Grant, Sherman, Thomas, and a host of his distinguished children well known to fame.

In defense of his country's reputation, whether at home or abroad, Mahan, with his incisive pen, ever stood forth a champion knight; and in our civil strife, though reared in a seceding State, no utterance escaped his lips but of loving loyalty to that flag he so revered for threescore years and ten.

Such were the productions of his prolific pen, which have given him a world-wide reputation, and placed him in the foremost ranks of erudite engineers and eminent savants. Appreciating his attainments and honoring themselves, institutions of learning bestowed upon him their highest distinctions. Both Brown and Princeton conferred the honorary degree of A. M., in 1837; and William and Mary, Brown, and Dartmouth each gave that of LL. D. In 1828 he was elected a Member of the Geography Society of Paris, and since of many scientific associations in the United States, particularly of the National Academy of Sciences, of which he was one of the original fifty corporators.

 p323  Besides these academic recognitions of his worthiness, his professional opinions were often sought. In 1850 the Governor of Virginia appointed him to decide the vexed controversy between the litigants regarding the location of the great railroad bridge at Wheeling, Va.

But it is on his professorial capacity that his fame chiefly rests, especially with the graduates of the Military Academy, all of whom, living when he died, save about 130, were educated by him in civil engineering, architecture, stereotomy, military engineering, and the science of war. As a professor he had a threefold relation: first, to his pupils; second, to his assistants, who were detailed to assist him in the instruction of Cadets; and lastly, as a member of the Faculty of the Military Academy.

To his pupils he was not simply the learned teacher, but the disciplinary officer and high-toned gentleman. When he entered the recitation room of Cadets, they involuntarily straightened up and sharpened all their faculties, sensible that they were to undergo the precise movements of a mental drill. Never for a moment were the relations of the inferior to his superior allowed to be forgotten, nor the most rigid requirements of military subordination to be relaxed. All points of etiquette and every exaction demanded by regulations were strictly enforced, not only to impress his pupils with the necessity of wholesome discipline, but to cultivate in them the manners and habits which should ever characterize officers, — gentlemanly deportment, strict integrity, devotion to duty, chivalric honor, and genuine loyalty. These essentials of a trustworthy soldier he assiduously instilled in the minds of Cadets, as many graduates can testify when they revert to some vital precept inculcated by that excellent officer and noble man. Great, however, as he was in moulding the actions and characters of his pupils, he was greater in instructing them. He had an almost intuitive perception of the exact amount of information possessed by each on the subject-matter of the lesson in hand, and by a few dexterous questions would quickly winnow the kernel of knowledge from the chaff of pretension. All shams were mercilessly exposed by his keen and telling criticisms, and few brains escaped his piercing probe. Sometimes, perhaps, he was a little captious in irritable, but it must be recollected that with broken health the mind becomes sensitive to trivial offenses, and is apt to magnify them into real affronts. But however sarcastic he might appear, his severity was not designed to wound his pupils nor do them any injustice. If the difficulties of the lesson were too great to be overcome, the Professor was ever ready to explain all its intricacies, and with his skillful analysis give it a new portraiture clearly photographing it to the comprehension of the student. In this power of analysis, sharpened by critical study and laborious research, he was an accomplished master. Especially did he possess it in the consideration of a siege, a battle, or a campaign, which in his hands, from what appeared to be a complex jumble of chance events, became a striking illustration of the true principles of tactics and strategy. With what pleasure and profit can graduates, particularly those of later years, recall his graphic pictures of the battle of Leuctra, where epam won such unfading laurels; of Scipio's destruction of the Carthaginian power on the fatal field of Zama; of Caesar securing the empire of the Roman world at Pharsalia; of Frederic's masterly success at Leuthen; of Napoleon's wondrous campaigns in Italy, Germany, and France; and of our mighty contests at get, Vicksburg, Nashville, along the death-strewn march to Atlanta, and in the giant struggle from the Rapidan to our crowning triumph at Appomattox!

But it was especially the privilege of the young officers of engineers who were detailed as assistants to this learned professor and eminent educator to profit by his treasured stores of knowledge, to learn his skilled methods of educating youth, to discover that the goal of success is only  p324 reached by patient toil, to feel the influence of his example, which by faithful service had built up an enviable reputation, and to enjoy the friendship of one who rarely engrafted his affections except upon true merit.

As a member of the Faculty at West Point, his whole aim was to advance the prosperity of the Military Academy, to keep it up to the highest standard as an educational institution, to preserve its reputation as the first scientific school in the land, to render it worthy of the nation of whose military glory it was the custodian, and to graduate honorable men, accomplished scholars, and finished soldiers. For these ends he was ready to make any sacrifice, to suffer even in health, and to labor without limit. Those who have been associated with him on the Academic Board well know his bold advocacy of vital principles, his manly opposition to all technical influences, his inflexibility of character in maintaining the right, and his singleness of purpose in supporting the best interests of the institution. Any assault upon the Academy he felt as keenly as a thrust at his own reputation, which he quickly resented with all his mental might; and his noblest pride was awakened and his joy unbounded at every evidence on the part of its graduates that they had profited by the teachings of the institution and won laurels for their Alma Mater.

Such was this model professor, who for forty academic years had patiently implanted the principles of engineering and the art of war in the minds of about two thousand pupils, who had devoted nearly all his hours not in recitation to the study of his profession, and who denied himself even healthful recreation that he might have more time to endow his department with the wealth of his intellectual riches. Rarely did he take a day's leisure from his duties, or even hours from close application, except on Saturday evenings, when his constant practice was to relax his routine of labor at Cold Spring, in the hospitable mansion of Mr. Gouverneur Kemble, or "old Uncle Gouv," as he is more fondly called by all the graduates of the Military Academy, to whom he has ever been the genial, generous friend, and of their Alma Mater a steadfast supporter for more than half a century. During the summer encampment of Cadets, though on leave of absence for recruiting tired nature, Mahan would often spend his entire vacation in examining fortifications, harbor and river improvements, and other public works, that he might profit by the experience of educated engineers to enrich the West Point curriculum. In these summer tours he rarely omitted a visit to General Thayer, the venerated "Father of the Military Academy," to pay his personal homage of affectionate regard, and confer with him upon all pertaining to the welfare of the institution of which he had planted the precious germ that has brought forth such golden fruit. None more than Mahan appreciated the inestimable value of the services to the whole military profession of this great Superintendent of the Academy, under whom he had been educated, and none more worthily wore his mantle than he who had so long been his eldest child at that institution which has been the guard and glory — presidium et decus — of our arms.

Mahan bore unusually well the fatiguing ordeal of the last June examination of Cadets, and at its close was anticipating the repose of his summer relaxation when it was disturbed by rumors that the Board of Visitors had recommended his retirement and disconnection with the Academy. It is true that he had passed the age when Army officers are usually withdrawn from active service, but the President, who had been his pupil, and well knew that his intellectual vigor was unimpaired, had exercised a wise discretion allowed him by law in continuing this trusted professor in a position he had so long and so ably filled. Though he had nearly reached the Psalmist's span of life, he was yet mentally young, — younger than Nesselrode when at the head of the Russian ministry, or  p325 Gortchakoff, late in that responsible position; than Thiers, when he was the ruler of France; than Metternich when he held his iron rule over Austria; than Palmerston or Russell when controlling England's destinies; than Wellington and Radetsky when exercising supreme military command; or than Blücher or Moltke when conducting colossal campaigns.​a

These reports as to his retirement, over which he continually brooded, soon settled into positive knowledge by the publication to the world of the report of the Board of Visitors. The effect upon him, who had been so long identified with the prosperity and success of the Military Academy, and whose attainments and devotion had so greatly contributed to its proud pre-eminence, was most melancholy. Of delicate frame and with a highly nervous organization, he was peculiarly susceptible to the power of such an unexpected blow. At his age the physical constitution cannot well contend with acute mental distress, as was evident with him when in the beginning of September he entered upon the instruction of his forty-second class in engineering. It was painfully manifest that the fatal shaft had entered his brain, as in occasional paroxysms he gave unmistakable signs of mental aberration.

By the advice of his wife and friends, he reluctantly and with feelings of deep dejection left West Point by the steamer Mary Powell, in company with a faithful inmate of his family, for the purpose of consulting Dr. Gray, of New York, who had long been his trusted physician. Some time after leaving the wharf, while he was promenading the steamboat's deck for exercise, his companion urged him to put on his overcoat, as the morning was chilly. Cheerfully he complied, and was easily induced soon after to go into the forward saloon. While seated here he complained of being too warm, and removed his rubbers and overcoat. Shortly he was noticed to rest his head in both hands as if in great agony, and his legs to twitch convulsively. While thus suffering, probably from one of his acute paroxysms, by which he was bereft of reason, he suddenly rose, passed through the saloon door, which was quite near, and in his frenzy going to the side of the boat, just in front of the port wheel-house, he was suddenly in the jaws of death, — his body to the watery deep, and his soul to the heaven above.

Thus terminated the tragedy of life of this world-renowned man; the erudite engineer, whose study was to emulate the great masters of his profession; the accomplished scholar, the sweet food of whose mind was gathered in the richest fields of science; the skillful educator, whose glory was to rear soldiers worthy of the Republic; the conscientious officer, who resolutely labored to secure the ends for which he was appointed; the pure patriot, who best served his country in her darkest hour; the upright Christian, whose tone of sentiment was lofty and sincere; the courteous gentleman, whose suavity was the rival of his modesty; the trustworthy friend, whose affection, though not of hasty growth, was lasting when worthily bestowed; the fond father, devoted to his children's welfare; and the loving husband of the congenial partner of all his joys and sorrows.

Like the great actor who had well played his part and won the plaudits of all, it was not his to choose in what part of the drama of life he had to make his final exit. He now sleeps in the shadow of his own academic groves, yet lives one of those

"Who leaves a deathless name behind —

Friends of the world, and fathers of mankind."

Thayer's Note:

a The best example of all is that of the 6c Byzantine general Narses, who achieved some of his greatest military successes when he was in his mid-eighties.

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Page updated: 27 Nov 10