I’ve mentioned on several occasions how the lessons on fortifications, used to teach cadets, demonstrate the evolution of doctrine from pre-war thinking into the post-war era. We see some of this evolution when comparing pre-war and post-war versions of Mahan’s treatise. But where the changes really come into play is when comparing Wheeler’s 1880 textbook.
An example of these changes is how Wheeler chose to relate details of interior arrangements. Even when classifying these arrangements, Wheeler offered a shift, sometimes subtle, change of focus. Recall Mahan’s pre-war text described the classes of interior arrangements as such:
The class of constructions required for the above purposes, are batteries; powder magazines; traverses; shelters; enclosures for gorges and outlets; interior safety-redoubt, or keep; and bridges of communication.
Somewhat brief, and from there Mahan proceeded to detail how batteries were placed on the parapet… with emphasis on the employment of artillery.
Wheeler offered a similar set of classifications, but abstracted those a bit with a mind to functional requirements:
Classes. – The earth work for the parapet being completed, and the revetments of the interior slope constructed, attention is then paid to the interior of the work. Certain arrangements have to be made in the interior, to add to the efficiency of the defense, and to provide for the comfort of the troops who have to occupy the work. These interior arrangements are divided into classes, according to the object to be attained by them.
The divisions may be classified as follows:
The arrangements of, and along a parapet, intended to add to the efficiency of the defense;
The arrangements within the area enclosed by the parapet, to shelter the men and matèriel from the fire of the enemy;
The arrangements made to allow egress and ingress of the troops; including those made to guard the outlets against surprise; and
The arrangements which may be made to provide for the comfort and welfare of the garrison when occupying the interior of the work for some time.
While Mahan named specific structures that would be constructed within the interior, Wheeler’s classifications come across is more so proper doctrine. In other words, Wheeler put the reason before the task. Such is a more formal approach to doctrine, as opposed to simply providing a list of structures, and their specifications, to be used.
And with that approach, abstracted from naming particular types of structures, Wheeler was able to identify some of the needs, beyond the basics, of a garrison occupying a fortification. You know… like those “comfort and welfare” things he mentions. But not to be overlooked, shelter from enemy fire and ease of entry or exit. These were all things Mahan addressed, but gave limited treatment. Did Mahan simply not care about the troops? No. But Mahan’s text was rooted in some pre-war concepts which, though we have discussed before, should be repeated for clarity.
Mahan’s instruction about fortification borrowed heavily from the European experience. It was a textbook on field fortifications which would complement other instruction relying heavily, as is often the case with military science, on the “last war.” Many scholars have debated the influence of Antoine-Henri Jomini on Civil War generalship. But I don’t think we can dispute a “what would Napoleon do?” approach prevailed.
That in mind, the military minds came to make several operational assumptions. With respect to fortifications, the assumption was two types would be employed. Fixed, permanent fortifications were constructed to defend vital areas. For the Americans, these were most often seacoast fortifications, as most potential adversaries would need to gain lodgement at some port (the exception, prior to the 1840s, being the northern border, but even there the great lakes presented a seacoast-like need).
The other form of defense assumed was temporary or field fortifications for use by an army on campaign. And those were intended to work within the tactical framework handed down by the European experience on the Napoleonic battlefield. These fortifications were employed to protect important areas related to the army’s campaign objectives. And those objectives were subject to change. The design of the works was more so to deter direct attack. In that way the temporary works would deter direct attack, requiring a deliberate effort (i.e. a siege or other significant commitment of resources). The temporary fortification was not designed for prolonged occupation or lengthy defense. Above all, the temporary fortification was always a function of the campaign being undertaken at that moment in time.
The American experience, even before the war, offered a slight twist to the paradigm. With a significant commitment to the frontier, structures such as blockhouses became important. Yet the US Army did not give much instruction to that part. In my opinion there were two significant reasons for this. First, perhaps foremost, the methods for establishing frontier garrisons were judged as intuitive. Mahan’s “Outpost” manual covered some of this. Secondly, much of the responsibility for these frontier garrisons was given to territorial, state, or local authorities. In short, it was not a major mission in the broader sense. Rather, the US Army was supposed to give Congress detailed plans for defending the coast. Those commitments out west were not the “big show”.
Civil War experience demonstrated the “two types of forts” assumption to be incorrect, to say the least. Operational requirements demonstrated there was a third type which fell directly between the chairs. That being a semi-permanent fortifications which were not directly tied to ongoing campaigns. The best example of that would be the Washington defenses. Lesser so the Richmond defenses, but of course those became the focus of a campaign later in the war. Other examples, which we’ve mentioned in relation to blockhouses, were those works constructed to protect communications and supply lines. All of which supported the army in the field, but were not a direct function of that army’s operation… i.e. the campaign. And as a function of those requirements, the engineers had to address other needs within the fortifications, to include “comfort and welfare.”
What I like about the passage from Wheeler enumerating the classes of interior arrangements is that he removed a lot of the Napoleonic baggage from the discussion. Sure, forts were still built in the manner employed in the first quarter of the 19th century. Men used shovels to dig, then pile the earth. Fortifications still required parapets and ditches to be effective means of resistance. The “physics” of the matter did not change, other perhaps than the need for additional thickness to resist rifled projectiles. But it was the requirement those fortifications were filling that shifted over time. That’s what I see reflected in the approach Wheeler gave to these particulars.
(Citations from Dennis Hart Mahan, A Treatise on Field Fortifications, New York: John Wiley, 1852, pages 51-2; Junius B. Wheeler, The Elements of Field Fortifications, New York: D. Van Nostrand, 1882, page 114. )