We’ve discussed at length that Mahan felt artillery was the “principal part” of the defense. But on the offense, did the artillery play a minor role? Not according to Mahan. We sometimes misconstrue the notions about supporting roles to be of lesser importance, or perhaps inconsequential. Mahan felt the artillery’s support was vital to staging a successful attack. So how to go about constructing a successful support? Turning to the classes of artillery in use at that time (pre-Civil War), Mahan proposed different roles for heavy and light guns:
In the onset of offensive movements, good positions should be selected for the heaviest pieces, from which they can maintain a strong fire on the enemy until the lighter pieces and the columns of attack are brought into action. These positions should be taken on the flanks of the ground occupied by the assailant, or on the centre, if more favorable to the end to be attained.Mahan, 61.
Consider a generic scenario, what I call the “blackboard topography.” One might select good artillery positions on the flanks, or the center as Mahan proposes. But regardless it is the heavy, long-range guns that are chosen to open the attack. And we need to understand, tactically, why this is significant. Having the least mobile component of the army as the base from which the army can launch an assault makes good sense. More so having those long-reaching and hard-hitting guns opening the engagement at a range from which only the enemy’s peer heavy guns could respond.
And at what range should those heavy guns open? Mahan did not delve into the technical details in this passage. For the most part, he left those things open as such was the domain of the artillerists and subject to change as the technology evolved. Though we can say given the pre-war context, I would offer 1200 yards. That was the effective range of a 24-pdr field howitzer firing shell. And that particular caliber and class would be the shortest-ranged of what was considered “heavy” artillery in the 1850s.
Continuing on in that paragraph, we put some weight… emphasis… on that point. The enemy would certainly respond to this opening bombardment:
In all cases, wide intervals should be left between the heavy batteries and the other troops; in order that the latter may not suffer from the return fire which the assailed will probably open on the batteries. For the same reason, care should be taken not to place other troops behind a point where they would be exposed to the return fire of the assailed; when this cannot be avoided, the troops should be so placed as to be covered by any undulation of the ground; or else be deployed in line to lessen the effects of the shotMahan, 61-2.
Those heavy batteries are going to be magnets for the enemy’s attention. And that in mind, there appears an additional factor here beyond just the measure of range and weight of metal. Not only does the opening bombardment damage the enemy directly … “kinetically” as the modern military is fond of saying… but also by splitting the enemy’s attention in response. Again, “blackboard topography” here, but opening the engagement with those big guns ensures the enemy must respond and counter the bombardment… and thus redirects defensive firepower that would otherwise be applied to the infantry or cavalry.
And in the study of assaults staged during the Civil War, we see this play out time and time again in the form of artillery duels. Most students will recognize the preparatory effects to damage the defense. However, consider how those duels usually played out. Particularly where ammunition supplies factored into how long the bombardment could be sustained. Do we know of instances where a defender deliberately ceased counter-battery fire in order to save guns and ammunition to repel the infantry? Yes we have. So this is not just were the defender pointed those cannon, but also if he decided to fire them or not.
But what of the light artillery?
The artillery which moves with the columns of attack, should be divided into several strong batteries; as the object in this case is to produce a decisive impression upon a few points of the enemy’s line; by bringing an overwhelming fire to bear upon those points. These batteries should keep near enough to the other troops to be in safety from any attempts of the assailed to capture them. Their usual positions will be on the flanks and near the heads of the columns of attack; the intervals between the batteries being sufficient for the free maneuvers of the other troops, in large bodiesMahan, 62.
This, readers, is about as close as Mahan comes to any notion of “artillery charges.” The notion here is to carry forward, with the assault force, an artillery component up to a point, while still out of musket range, where direct damage can be done to specific enemy positions. Since these light batteries at the time Mahan was writing would be armed with 6-pdr field guns and 12-pdr field howitzers, the idea range would be 1000 yards. Perhaps closing up to 700 yards if the commander wanted to push things. Closer than that and that safety clause comes into risk, as the enemy infantry might be able to close quicker than the battery could respond.
I would stress the fire effects desired here. While none were articulated for the heavy batteries, the light batteries were there to do damage specifically to selected points of the defense. It was the light artillery that was to beat a path for the infantry and artillery. Consider also the control of these two elements of artillery. While the heavy artillery was far enough back to receive direction from the army commander (or at least the commander of the field), the light batteries were so far forward that only the assault force commander could exert any immediate control.
Note also the emphasis placed upon keeping open maneuver space for the infantry or cavalry. Very important to ensure the attacking ranks arrived at the point of contact in an orderly formation.
Continuing on, Mahan wrote:
The maneuvers of these batteries should be made with promptitude; so that no time may be lost for the action of their fire. They should get rapidly over unfavorable ground to good positions for firing, and maintain those as long as possible; detaching, in such cases, a few pieces to accompany the columns of attack. In all the movements of the batteries, great care should be taken not to place them so that they shall in the least impede the operations of the other troops.Mahan, 62.
This was the reason artillery batteries drilled hard on maneuver, being able to quickly place and unlimber. This point is lost sometimes on our battlefield walks, as we see the guns (if guns are indeed on the field to represent) sitting as if ready for action. I always stress this to any audience I’m leading on a battlefield tour. Maneuver of a battery was an intricate choreography.
As for a section or battery accompanying the assault force right into the attack? Some will contend here’s that mythical “artillery charge.” No, not so. These cannon were reserved to go into action once the objective was attained. A hedge against an enemy counterattack. And we might say, while such was fine for the 1840s and 1850s, during the Civil War rarely would such an accompanying battery move with the assault. At Belmont, early in the war, the Chicago Light Battery was thrown in with the initial Federal attacks. And later in 1863 on Grant’s Vicksburg Campaign, there were a few instances where artillery came into action with the initial infantry waves. But these were, I think, less so much U.S. Grant (or.. .gasp.. John C. McClernand) applying Mahan’s accompanying batteries to practice. More so that artillery in a mixed line of march were employed at the onset of a meeting engagement.
So why was the accompanying battery disused? Well, to be honest, we might also start questioning the notions about the heavy and light battery employments. In the first place, by 1861 the US Army was already shedding the designations of heavy and light within the field artillery. The 12-pdr Napoleon was the weapon of choice in what would become, basically, all-purpose batteries. Furthermore, the introduction of better fuses (Bormann, in particular for the smoothbore) gave better accuracy. Not in terms of aiming, mind you. Rather in the ability of the gunner to have the shell or case shot explode at the right time of flight in order to achieve the desired fire effect. With that ability in hand, why press the issue at any range less than 1000 yards? Double down with the rapid adoption of rifled guns at the start of the Civil War.
With that said, the question always arises of the impact of the rifled musket with respect to artillery use. I have always contended first and foremost that infantry musketry techniques didn’t change significantly with the adoption of the new technology. Infantrymen were not trained, as a rule, to engage targets out to the effective range of their weapons. Some sharpshooters, maybe. But not the rank and file. Nor were infantry commanders apt to open volley fires out beyond a few hundred yards. So how would that impact the use of artillery?
It didn’t. Rather, the reason we see a departure, particularly in regard to the offensive use of artillery, from the Mahanian concepts presented in Outpost was because of the advances in artillery technology. Taking advantage of lighter, longer-ranged, more accurate weapons, practitioners of the artillery (thinking names like Gibbon, Hunt, Barry, and others) began to relook the way their arm could be employed.
(Citations from Dennis Hart Mahan, An Elementary Treatise on Advanced-guard, Out-post, and Detachment Service of Troops, and the Manner of Posting and Handling Them in Presence of an Enemy, New York: John Wiley, 1861, pages 61-2.)