Mahan, Dennis Hart

(1802–71)

U.S. Military Academy Professor

Dennis Hart Mahan was the most influential American military thinker of the first half of the 19th century. His writings were the first significant attempt to make the principles that guided the Western way of war accessible to an American audience. In addition, his work as the preeminent member of the faculty at West Point and, more specifically, as professor of engineering and the art of war, played a significant role in shaping and fos-tering the professional sense that developed within the U.S. Army officer corps during the decades preceding the Civil War.

Mahan was born in New York City on April 2, 1802, although he spent most of his childhood in Norfolk, Virginia. Initially interested in a career in medicine, Mahan ultimately decided to enter the U.S. Military Academy in 1820 to take advantage of its courses in drawing, which he had become interested in while studying medicine. However, Mahan's affinity for mathematics quickly attracted the attention of the faculty, especially Superintendent Sylvanus Thayer; by the end of his second year at the Academy, Mahan was serv-ing as a mathematics instructor.

Mahan graduated at the top of his class in 1824 and received a commission in the elite corps of engineers, but, at Thayer's suggestion, he remained at West Point as an instruc-tor. Two years later, Thayer decided that Mahan should go to Europe to further his study of engineering. After a four-year stint in Europe, where he spent most of his time studying French military institutions, above all the School of Application for Artillerists and Engineers at Metz, Mahan returned to West Point in 1830. After a brief period as acting professor of civil and military engineering, he became a per-manent professor in 1832 and soon thereafter modified his title to professor of engineering and the art of war.

When Mahan was a cadet at West Point, the antebellum Army was at the tail end of an era of reform whose objective included developing a greater sense of professionalism in the officer corps. As a member of the faculty at West Point, Mahan helped future officers gain a firm grounding in the technical aspects of war. He concluded that the literature on this subject was insufficient for American officers to achieve the highest peak of professional development. Consequently, he produced a prodigious body of scholarship on military subjects that included Complete Treatise on Field Fortifications (1836), Summary on the Cause of Permanent Fortifications and of the Attack and Defense of Permanent Works (1850), and An Elementary Course of Military Engineering (2 vols., 1866–67). His most important and best-known work was An Elementary Treatise on Advanced-Guard, Outpost, and Detachment Service of Troops, With the Essential Principles of Strategy and Grand Tactics. First published in 1847, this book—popularly known simply as Outpost—not only was used at West Point, but also became popular with American militia and volunteer units.

In addition to his accomplishments as a scholar, Mahan was recognized as the most important member of the faculty at antebellum West Point. Not only did his class in civil and military engineering become the capstone course for cadets, Mahan also quickly assumed leadership of the Academic Board that governed the Academy. Under Mahan's guid-ance, the board was a bastion of conservatism that resisted any challenges to the culture and curriculum that Thayer had established while superintendent.

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