Mahan on Artillery Tactics, Part 4: More on the Defense

Let us continue the discussion of artillery as used on the defense, according to Mahan. And we again turn to Chapter II, verse 151…..

Those positions for batteries should be avoided from which the shot must pass over other troops, to attain the enemy. And those should be sought for from which a fire can be maintained until the enemy has approached even within good musket-range of them.

Outpost, 60-1.

Common sense at play here. Fuses are not fail-proof, no matter how good the quality control is at the arsenal. Short rounds were a concern then as they are today. A further concern was the ballistic path of the sabot used behind many projectiles. Though made of wood, that could still injure or kill. With the introduction of rifled guns, another concern entered play – the lead or soft iron sabots often sheered off after the projectile left the muzzle. Those fragments took less predictable paths.

The other part of this is the desired effect of allowing the cannon to engage right up to… and inside of… musket range. The “skirmisher” community will note that Mahan was writing this passage before the rifled-musket was in widespread use. However, we should note that well into the Civil War, 100 yards was still considered the effective range of those rifled-muskets, as the practitioners were focused on volley fire effects as opposed to the effective range of individual weapons.

Where the wings of a position are weak, batteries of the heaviest caliber should be placed to secure them.

Outpost, 61.

Another sensible suggestion here. But one that must play with earlier passages that dictated the bigger caliber pieces be placed on “the more retired points” as opposed to advanced positions. Looking back at the “taking away a course of action from the enemy” mindset, those batteries assigned to support the flanks would be there to remove an option to attack on a flank. Such implies, generally speaking, that in the defense the flanks should be tucked in or refused. I would not argue against that as a general application, but certainly not submit flanks should always be refused. Given terrain or other factors, one might extend a flank position to cover the front of the main defensive line…. you know… like in those simple entrenchments that Mahan wrote of in other volumes.

Thus far, Mahan has placed the light batteries (shall we say the “mounted” batteries?) and the heavy (or “foot”) batteries. What about the horse artillery?

A sufficient number of pieces – selecting for the object in view horse-artillery in preference to any other – should be held in reserve for a moment of need; to be thrown upon any point where the enemy’s progress threatens danger; or to be used in a covering the retreat.

Outpost, 61.

Stomp your feet here to ensure all the cavalrymen hear and heed this. Horse artillery, in the defensive, was not simply attached to the cavalry for support of the troopers doing what ever it is they do on the defensive. Instead, the horse artillery was a reserve force to be used when pressed. If we turn again to “taking away courses of action” then here we are considering how an enemy commander would follow up behind initial success. If that assault has indeed achieved a lodgement on the main defensive line, the next step would involve pressing reinforcements forward to enlarge gains and break the line. The counter, Mahan proposes here, is the rapid, flying batteries of horse artillery introduced to seal that fissure.

And if that cannot be attained, at least have those horse artillery batteries in position to dissuade the enemy from following up with a close pursuit. A handful of well placed shells from the horse artillery should at least cause pause.

Everything thus far we might summarize as “use common sense and good judgement.” But the next paragraph is where the armchair generals will set up and start typing comments….

The collection of a large number of pieces in a single battery, is a dangerous arrangement; particularly at the onset of an engagement. The exposure of so many guns together might present a strong inducement to the enemy to make an effort to carry the battery; a feat the more likely to succeed, as it is difficult either to withdraw the guns, or change their position promptly, after their fire is opened; and one which, if successful, might entail a fatal disaster on the assailed, from the loss of so many pieces at once.

Outpost, 61.

Yes, at first glance, Mahan is laying out an argument against massing artillery on the battlefield. And our latter-day Stonewall Jacksons are quick to point out massed artillery is often the key to victory!

The important part of this passage is “large number of pieces in a single battery.” This is a “battery” not as an organizational unit, but as a position. Reading as such, this is a warning about putting multiple batteries in one contiguous position. If those guns are not arrayed as discussed at earlier points in this discussion of artillery on defense, then such a collection would be a vulnerable, tempting target. Placing the guns hub to hub is not “massing the guns.” But arranging those guns, in accordance to the guides presented by Mahan, is.

What I’d contend is that Mahan was not arguing against what Henry Hunt would do at Malvern Hill. Just the opposite. Prior to July 1, 1862, Hunt organized and emplaced the artillery into a fine example of what Mahan encouraged through these couple of pages on defensive arrangements. Go through the checklist – good engagement ranges, cleared fields of fire, complementing postings, light batteries advanced, heavy batteries retired, wings protected, infantry kept clear of the guns, and all well supported. And that arrangement allowed Hunt to introduce fresh batteries and withdraw tired ones, with relative ease. Thus, what Hunt had at Malvern Hill was not a “large number of pieces in a single battery” but instead a massing of combat power on a good position which maximized the capabilities of the artillery. Famously, one year and two days later, Hunt will accomplish the same feat on another battlefield while defending Cemetery Ridge. We might easily turn to the other side of the war and point to good use of massed artillery at Fredericksburg.

I think what Mahan is arguing against in this passage is actually instances like Missionary Ridge. One might say the Confederate artillery positions on that ridge were well placed for a siege in which their fire would be focused on distant Federal lines. The problem was no proper adjustment was made when that position transformed, due to the shifting of tactical situations, to a defensive one. And so that checklist that Hunt met on those hot July days was not met on that autumn day outside Chattanooga – dead space under the guns even past musket range, no complementary postings, no advanced or retired positions, infantry lines interspersed with the artillery, and little room to move the batteries around. And if we circle back to the “taking away a course of action from the enemy” notion here, I’d posit this counter-intuitive thought with a wry smile: the position on Missionary Ridge was so bad that it invited Federal commanders to accept and pursue a direct assault as a course of action. And as a demonstration, at that!

The last paragraph in this section on defensive arrangements for artillery strikes to the logistics of keeping those guns feed:

In all defensive dispositions the ammunition should be most carefully husbanded. A fire should never be opened until the enemy is within good range; and, when once opened, be continued with perseverance and coolness up to the last moment in which it can be made effective.

Outpost, 61.

I’ve mentioned this a time or two before, expressed as “staying power” of the guns. By this I mean the time for which the gun can remain at a position and actively part of the battle before having to replenish ammunition. Obviously many factors come into play here. Not the least of which is the number of rounds in the ammunition chests (in other words, the smaller-bore weapons had more rounds to shoot, all things being equal… yet another reason to have those big guns at retired positions). As we alluded to above (and at other places on this blog), Hunt and other good artillery commanders mitigated this with a good system to rotate batteries in and out of the line. Hunt also devised a very healthy system to push full ammunition chests up to the points where needed. Such adds another requirement here to those “good position” checklists, in that we must also consider allocating space to allow all the traffic needed in order to maintain a position “up to the last moment.”

And I stress “staying power” over perhaps the cyclic rate of fire. More so than simple weight of metal, it was the paced, deliberate, and measured fire which was desired. So let’s cast off these notions that artillery was just there to belch out canister, send smoke into the air, and make a lot of noise. The impact of those big guns, particularly on the defense, was to shape the flow of the battle… taking away courses of action available to the enemy.

(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 60-1.)

Case shot and practice of fire: A conundrum?

Consider this figure:

OwenPlate20Fig6

This particular figure appeared in “Elementary Lectures on artillery: Prepared for the use of the gentlemen cadets of the Royal Military Academy” by Captains Charles Henry Owen and Thomas Longworth Dames, published in 1861.  And as “Royal” implied, these were English officers and not Americans.  Still, the technology was the same and applied in much the same manner.  It is similar to illustrations appearing in American texts of the same period.  I simply chose this source because the basic illustration was cleaner.

Basically, this illustration explains the practice for firing shrapnel.  The target, on the far right, is a box labeled “Column of Men.”  And we see four examples where shrapnel was fired.  Only one of which was accurate and would achieve the desired result.  Labeled “a”, I’ll put a star on that point and show the respective coverage of the balls after bursting:

OwenPlate20Fig6A

The perfect shrapnel burst – at the right time of flight; at the right height; at the right angle of flight.  The momentum of the shrapnel shell (case shot… for us not subject to His Majesty) imparted forward progress to the balls after the burst.  So we see the expected pattern would place fragments and balls across the formation of infantry.

If the the fuse was set for too short a time of flight, then the shrapnel burst too soon.  At this case, point “b”:

OwenPlate20Fig6B

The payload falls well “short” of the target. Not to mention, and not depicted here, it was also possible for the burst to be “long”, with the payload landing well beyond the target.  So setting the fuse

But the fuse timing was just one of :

OwenPlate20Fig6C

Or if the projectile is fired too low:

OwenPlate20Fig6D

This brought the burst too low and well in front of the target.

Not illustrated in this figure is the angle of flight.  But you might get a feel for that looking at bursts “c” and “d”.  However, as case shot/shrapnel was fired primarily from guns, sometimes howitzers, and not mortar.  So this was somewhat a “goes without saying” consideration.

Still we see depicted two of the three necessary components of a proper shrapnel burst.  The right height being the darkest of the three trajectories depicted.  We see points “a”, “c”, and “d” being the right time of flight.  Allow me to “box” these to highlight:

OwenPlate20Fig6X

Hopefully nothing entirely new to artillery enthusiasts.  Just depicting the desired work of the shrapnel… er… case shot… in combat.  As we well know, the artillerist would need estimate the range to target.  From that, he would derive the necessary elevation.  That, of course, considering the desired height of burst.  And the artillerist would need to calculate time of flight to the optimum bursting point.  That being used to properly cut or set the fuse.   And…. goes without saying the artillerist would also need to point the gun toward the target (a factor not easily depicted in the two-dimensional world of the illustration).

Great!  So the artillerist had to do a lot of computations in the heat of combat.  One might think the manuals would have a lot of tables and guides as to how one should compute bursting height and time of flight.

Given such complications, one might think that manuals of the period would devote much space to instructions.  Well…. The brand new “Field Artillery Tactics” of 1861, from the minds of William French, William Barry, and Henry Hunt, mostly covered how to maneuver the battery.  Though unofficial, John Gibbon’s “Artillerists Manual“, with a wealth of insight for the gunners to consider.  Yet it also lacks any details on the practice of firing case shot.  Even Owen and Dames, from which these illustrations are taken, did not discuss the practice in any length.  They felt an illustration would suffice, apparently.

These references would offer elevations, range, and, perhaps but not always, time of flight for selected weapons.  But none would offer details of the ballistic behavior for shrapnel at the point of the burst.   Such was not simply derived by extending the trajectory out to the ground.  Rather one had to consider loss of momentum of those balls, fragments, and sub-projectiles, which fell off at a greater rate than a complete projectile.  And I’m just scratching the surface of the data needed for one to compute a “good” firing of case shot.

There are very few recorded experiments conducted at the time to learn how case shot behaved (Dahlgren’s experiments for boat howitzers come to mind, but there were some US Army and British experiments in this regard).  Yet, very little of what was learned went into the manuals.

That, I would submit, is a conundrum.

Canister and our silly notions about canister

It is my perception is that the average student of the Civil War latches on to some misconceptions about canister as used from field artillery.  And from that misconception, the student (buff, enthusiast, or even credentialed historian as it may be) carries forward to some misunderstandings as to how artillery was used on the Civil War battlefield.  Consider Paddy Griffith’s assessment:

The main effect of artillery came at what may be described as ‘canister range’ – the last 300 yards to the gun, sometimes extending to 500 yards. It was here that the flash and crash of the heavy Napoleons, firing two and a half pounds of powder with each detonation, could numb and stagger the enemy, even when they did not physically hurt him.

The sources provided for this observation is L. Van Loan Naisawald and Jack Coggins.  Now, Naisawald’s Grape and Canister is a good read on the artillery of the Army of the Potomac.  But it is dated (to be kind… I’ll leave it at that).  Coggins’ Arms and Equipment is a good premier for study, but not by any means authoritative on the subject of artillery.

I would say Paddy Griffith is not alone in this “weighted” assessment of artillery – and allow me to use “weighted” in two ways here.  Certainly weighted in the sense that canister was the artillery’s most effective projectile on the battlefield… and that the physical weight of the canister had some value against the infantry…. From that we see some historians attempt to devolve the tactical situation down to raw numbers:

Certainly the two Union artillery batteries had an impact, but the majority of fire came from the infantry. Artillery, even rapid firing double canister, would only be throwing 54 projectiles per tube per minute, (about 650 per minute for all twelve guns) and could keep that up only for a couple of minutes before they ran out of the proper ammo. 1000 infantry would add between 2000 and 3000 rounds per minute, assuming a normal rate of fire, and with 100 rounds apiece, and another 1000 men in support ready to step up when the front line emptied their boxes, the infantry’s fire could be sustained for a much longer time.

That quote is from a blog entry by Dave Powell from 2009.  In context, Powell was discussing a specific circumstance in the battle of Chickamauga in which the artillery was, due to the tactical setting, not employed in a location to take advantage of it’s full capabilities.  We might haggle over bad decisions by leaders on the spot, or discuss the finer points of the situation.  But that discussion starts with an assessment of what the artillery was there to do in the first place. That said, assessing the artillery’s potential killing power simply as a measure of the canister spread is to ignore 90% of the combat potential that artillery brought to the field.  And that, I would submit, is not how leaders of the time would weight their decisions regarding artillery employment.

Specifically toward that assertion, consider the standard load out of the 12-pdr Napoleon ammunition chest (since Paddy Griffith liked it) as configured according to Ordnance Department standards:

  • 12 solid shot
  • 12 spherical case (case shot as I prefer, but sometimes called shrapnel)
  • 4 shells
  • 4 canister

Multiply that times four, as a gun brought that number of chests into action between the limber and caisson, for a total of 128 rounds.  We see that canister constituted only 12% of the ammunition on hand, if we go by regulation.  However, we also know that in service many artillerists adjusted those quantities.  Henry Hunt, for example, before the Overland Campaign (and thus incorporating years of wartime service experience) suggested increasing the number of solid shot at the expense of case shot.  But at the same time he did not want an increase in canister.   So… if Henry Hunt, who we would all agree knew his business, felt that his gunners needed more solid shot, by a factor of four, than canister, what does that tell us about the preferences for projectiles on the battlefield? And furthermore, what does it say about how leaders wanted artillery to be employed?

Better still, let us turn to another authority on artillery… straight from the muzzle if I may … John Gibbon:

The kind of projectile to be used, will depend on circumstances.  Shot and shell should be fired against troops taken in flank or obliquely, against deep columns, and against artillery.  The horizontal fire should be used against troops advancing in mass to force a bridge or defile, or marching over very smooth ground.  Shot had better be used against infantry, and shells and schrapnell [case shot] against cavalry, as this latter arm presents the highest mark, and enables the pieces of the bursting shells to do more execution…. A charge, when within short range, may be received by firing from each piece a solid shot on top of which is placed a round of canister. the firing then as rapid as possible, sponging may be dispensed with, within 150 yards, and as the enemy approaches nearer, canister alone is used, pointing very low at very short ranges, so that the projectiles may ricochet and scatter more.  Canister should not be fired at distances greater than 300 to 400 yards. Shrapnell [case shot] should be used against troops deployed, or in column, by division or squadron.  Schrapnell and shells produce a greater moral effect, generally, than grape or canister.

Here we have clear guidance from one very well respected authority at the time.  We see “weighting” of the type of projectiles in the ammunition chest was indeed derived from the use preferences.  Those preferences were determined based on the intended employment of artillery on the battlefield.

Think about this – what was the artillery battery there to accomplish?

I’d submit that a short answer to that question is simply – to keep the enemy off targeted terrain.  Yes, the “ying-yang” of infantry and artillery.  Infantry was supposed to seize and hold terrain. Artillery was to keep the enemy off terrain (not necessarily to “drive him off” but where that tactical need was drawn…perhaps).  There’s more to it all, of course.  And I don’t wish to over-simplify where such carries perils.  But if we go back to the words of men like Hunt, Gibbon, Barry, and other artillerists from the war, we see that premise on exhibit.  Artillery was best used… intended to be used … in a manner to deprive the enemy of advantageous terrain.

We are coming up to an anniversary of a fine example of just how things “worked” in action.  Turn to June 30, 1862 and Battery G, 2nd US Artillery.  On that day, Captain James Thompson (another officer who knew quite a bit about how one uses artillery…) had orders to deploy his battery in what would become the battle of Glendale, or Frazier’s Farm:

In compliance with instructions from the general commanding the division the battery was posted on the right of the New Market road, supported by Berry’s and Robinson’s brigades, in order to be in position to open fire on the enemy advancing either upon the New Market road or upon the Central road.

Mission statement – Thompson’s battery would deny the use of those roads to the enemy. We may parse it all sorts of ways, but that is what the guns were there to do.  Not to hold ground.  Rather to keep the enemy from using specific terrain (roads) that would allow closer approach.

But… as in so much on the battlefield, not everything works according to plan:

About 400 yards in front was a dense wood, which approached within 100 yards on our right behind a small house. About 4 o’clock the enemy came upon us in line from this wood. I opened fire upon them with spherical case-shot, but they advanced to the débris of two fences I had caused to be thrown down in the earlier part of the day and about 100 yards in front. Canister was now used, and our supports opened fire on them with musketry, and they were stopped. The wood on the right was densely crowded with them in large force, and three successive charges to capture the battery were repulsed by the prompt and gallant supports deployed between the guns and by the murderous double canister from our guns, loaded without sponging.

So.. the Confederates were not so kind as to simply advance up the roads, but rather through the woods in front. But notice the selection of projectiles described.  Starting at 400 yards with case shot, the gunners only changed to canister when their adversary came within 100 yards.  It was self-defense range.  The frightful “double canister… without sponging.”

And the battery held its position, but not without great effort:

The battery was enabled to hold this position until about 8 p.m., after the capture of the battery on our left [Lieutenant Allen Randol’s Battery E and G, 1st U.S. Light Artillery, if memory serves], and until our supply of canister was exhausted, some guns having fired double spherical case-shot, cut to explode on leaving the gun.

To the point here, we can say canister was used with effect on that day.  But we also see that it was used for self-defense of the battery.  It was not the intent of Thompson, or any other artillerist on the field that day, to accomplish the primary mission by means of canister fire.  Just worked out the plan fell apart and weight of canister, along with some case shot, is what saved all but one of Thompson’s guns.

Likewise, we could roll forward one year and a few days to July 2, 1863 and consider several other batteries in tight situations using canister… some also employing double canister without sponging to speed the delivery.  But in all those cases we see a common underlying factor.  Like Thompson’s battery the year before, Captain James E. Smith’s 4th New York was not deployed on the Devil’s Den for the purpose of spewing canister at close range.  Rather it was placed with the intent to keep the Confederates off ground approaching the position.  Circumstances played out differently, as we well know.

Accounts from July 2 are filled with artillerists reporting canister at close range.  But that was an exceptional use on an exceptional day.  We need only say the words “Peach Orchard” and “Dan Sickles” to rejuvenate a 150 year old discussion of plans gone awry. You see, it was more exception than the rule that batteries would be “hard pressed” into self-defense using canister. Rather more often batteries would be employed to do as the artillery chief envisioned over longer ranges.  As such, the artillerists would accomplish their mission with shot, shell, and case. And, by design, that is what made up nearly 90% of the ammunition on hand.

(Citations, other than those linked above, are from  – Paddy Griffith, Battle Tactics of the Civil War, New Haven: Yale University Press, 1989, Page 170; John Gibbon, Artillerist’s Manual, new York: D. Van Nostrand, 1863, page 359; OR, Series I, Volume 11, Part II, Serial 13, page 172.)