This is the classic mid-19th century work on fortifications by the most distinguished professor of military engineering at West Point Academy, Dennis Hart Mahan. It is key to understanding the system of forts that developed in the early 19th century and provided the backdrop to much of the Civil War. Much of the material in this book was taken from materials taught by Mahan to cadets who later became officers in both the Union and Confederate armies. Revised in 1887 "with a view to rejecting only that which has become obsolete through the introduction of improved weapons and methods and to explaining and illustrating the new features developed from the sane causes."