This summer, while doing research at Stratford Hall, I happened across the name of one West Point professor who quite literally taught every cadet who fought in the Civil War. It is fairly common knowledge than many of the war’s great commanders were classmates together at West Point. For example, the class of 1842 contained George McClellan, James Longstreet, and John Pope. Such commanders influenced the course of the war by drawing upon their West Point education, and while they may have held different military outlooks, they all drew upon the teachings of one man: Dennis Mahan, professor of mathematics as well as military and civil engineering. Thus, Mahan, a relatively unknown figure, had a direct impact on how the war was waged during ...