Gettysburg, Day 3: Cannon Shells and Logistics

Preface: Sorry this is posted a day late. Intended for this to go live yesterday, but was too busy with other matters. Readers, hopefully, will understand… and enjoy the refinement that an additional day of rumination brings.

We hear this quip a lot: Military professionals study logistics! And as my theme in this Gettysburg series of late has been aimed at the importance of staff activities in relation to the battlefield, only natural that we should shift from intelligence and reconnaissance to logistics.

If I may again send a jab at the armchair general ranks here, everyone will agree logistics is an important facet to military operations, but so few really grasp the nature of logistics as a discipline within the science of military operations. That’s because we are a lazy lot. Logistics requires a grasp of details. One really has to dive into the numbers in order to understand the nature of logistics. It’s a whole lot of “left brain” stuff. More so than the average attention span is apt to allow depicted in… say… a movie… or even a blog post. But we will give it a swag here.

We often see logistics depicted in wargames as if a tether restraining a unit to its base of supply. In the Avalon-Hill-type games, often the rules (and optional rules at that!) specify the need for a unit to trace hexes back to a road, and thence back to a point of supply. And that might be the unit’s headquarters, a dedicated supply chit sitting on the map, or a hex location presumed to be a big pile of stuff. Regardless of the particulars, the rule presumes logistics is simply a flow of things which is regulated by distance more so than the resources involved. True, distances are an important regulator when discussing logistics. But that’s not the only regulator, nor is it the most important.

To study logistics, one has to understand and eventually master a vast set of formulas. If not precise algebraic formulas, not something far off that. But at the base, there are three basic foundations to any logistical problem:

  • How long will it take to get the needed resource (supply) from source point to issue point?
  • What resources are expended in order to get the needed resource (supply) across the gap from source to issue?
  • What is the value for the gaining unit with the issue of that resource (supply)?

I don’t mean to make this sound all Mahan-ish on you. But these are the basic measurements we have to somehow quantify in order to really understand the logistics. I’m not going to say this is the only way to quantify logistics. Just saying this is one approach, easy for those without a great deal of direct experience to grasp… and one we might directly apply to Civil War situations.

So… we need to know the time taken to move the supplies, as that will determine the lead time… or on the need end of the logistics, the wait time. We need to know how much the movement of the supplies will cost in terms of man hours, wear vehicle, gallons of fuel… or is that pounds of hay…, and any other resource allocation which is needed just to move the “stuff.” And the top end determining factor is what will the force receiving the supply be able to do once in possession of that supply which they cannot do without.

Very important point that last one. Nothing worse than opening a box of fancy hats at the moment one most needs bullets

More to the point, if you narrow down the military science to the measure of how much “combat influence” or “combat power” has unit has on the battlefield, then we are talking about things like the number of bullets per man that unit has. We logically move to a discussion of how long that unit can expect to engage in combat with the bullets on hand, given an average rate of fire. That then translates to a “value” of every box of bullets sent from the depot, which if we are bold in the calculus might translate to the number of minutes a unit can stand in a fight. And we can also determine how frequently those boxes should arrive.

We might argue for the infantry and cavalry some combat power remains even after the cartridge boxes are empty. Cold steel is bold, often dangerous alternative to hot lead. And for the artillerists, edged weapons are rarely an option.

Because this is “To the Sound of the Guns” and also because day three of Gettysburg features that great cannon duel, let us think about this in terms of artillery projectiles. Working backwards in the questions, as that allows us to progress from a firm footing for even those with a passing acquaintance with the battle, what is the unit of measure for cannon ammunition? Practically speaking it is this:

Taking a 12-pdr Napoleon, as in the illustration, there were 32 rounds in each chest. But remember not all rounds are equal – A dozen shot; a dozen case; four shells; and four canister. Each type with a different purpose. Indeed, let us set aside the four canister right from the start, as those were only for use at close range and, docturnally speaking, mostly for self defense. The combat power of the gun was derived from placing shot, case, and shell on a distant target. So lets trim that to 28 projectiles.. or 28 shots to be fired out of each chest.

Under a standard allowance, each cannon had four such chests – one on the limber, three with the caisson. So a total of 112 “value” rounds per gun, under the standard allocation of ammunition. Yes, keep in mind that is the “by the book” numbers. We know things were not so tidy in wartime situations (and if you didn’t know that, well… see all those numerous posts under the heading of “Summary Statements” here on the blog). But I contend those are good numbers on which to base a discussion.

Can we translate 112 rounds into the number of minutes a battery can be engaged before running out of ammunition? Yes, but we have to accept some complexities here. Obviously, if the intended target is enemy artillery (counter-battery fire which was the focus both ways on the afternoon of July 3) then solid shot might be more preferable, though case and shell had their place. Likewise, against infantry case was more applicable, though shot and shell had effects. Those preferences noted and considered, let’s keep the equation to a high level and go with 112 rounds… but reserve this line of thought for injection into the tactical situation at Gettysburg in a moment.

A really motivated crew might fire as much as two rounds a minute, but that’s not a practical rate. Brigadier-General Henry Hunt and other good artillerists are known to encourage slow and deliberate fires. And often we see that expressed as one round every two minutes. Some will cite higher rates sustained during the “hell on earth” minutes, such as occurred on the afternoon of July 3, 1863. No argument here. But I would simply point out the higher rate of fire usually translated to less accuracy, and thus a higher number of rounds expended to achieve the same tactical purpose, or worse leading to the failure to achieve the desired tactical purpose… as we shall see from the experience on the field that day.

So if fully stocked, by the book, a Napoleon gun could stand in battery firing one round every two minutes for almost four hours before needing some resupply. If doubled up to one round a minute, that’s at best a couple hours. Still we have a rough measure of one chest providing one hour of one gun’s worth of “combat power” of a crew firing “calmly and coolly.” Just a rule of thumb… not an exact measure by any means. If we change that to “frantic” fire, then one chest equals… maybe… thirty minutes.

Change the numbers a bit for a 3-inch Ordnance Rifle or 10-pdr Parrott. Those weapons had 50 rounds per chest. Subtracting back the canister again, just 46 “value” rounds (and remember that most of these light rifled guns did not have solid bolts issued at this time of the war – usually just case, shell, and canister). Thus translating to six hours of “time in battery.” At first this seems like a quantitative game changer in favor of the rifle. But as with all things logistical, gotta look at the details. A 12-pdr smoothbore shell and a 3-inch Hotchkiss weighed nearly the same (a little over 9 pounds). But the allocation of payload is different. Smoothbore shells were cavernous compared to the interior of rifled projectiles, and thus carried more “stuff” to the intended target. If we really want to “true up” this logistical measure, we’d have to gauge things like the number of balls in each case shot, by weapon caliber. Or perhaps the weight of the bursting charge in each type of shell. But for this lesson, at the 101 level, we save that for the advanced classes.

Now consider what we have discussed as would be applied to the situation on July 3. The Confederate gunners were attempting to suppress Federal firepower (artillery and infantry) lodged on Cemetery Ridge. The type of projectiles favored for that work were shells. Shot might help, but required very precise placement for effect. Case, designed to scatter sub-projectiles over a wide area, would have an effect. But it’s advantages were negated due to the limited depth of the target area. Shells, on the other hand, could have fuses cut to impart effects on a specific part of the defensive line. Thus, for Colonel E. P. Alexander the discussion is not about “value rounds” to derive combat power, but rather “preferred rounds” to achieve the desired effect from applying that combat power. Due to the tactical situation and fire effect preferences, he had but 16 “preferred rounds” per 12-pdr Napoleon and likely around 24 per Parrott or 3-inch rifle. Such limited his part of the duel from the “value round” figure of four hours down to only thirty to forty minutes of “preferred rounds.” Sure, he could (and there is some anecdotal evidence this was done) stockpile more shells in anticipation of the bombardment. But that would only correct the supply needs in the short term. And would have the additional effect of disrupting the normality of the issue of ammunition… by the regulation chest.

On the other side of the field, Hunt had a different set of criteria facing his logistic calculation. The initial targets were, just as his Confederate counterparts, enemy cannon. And again the shell was preferred for the work to be done. But Hunt also had to consider what the bombardment was designed to setup. The infantry were coming across that field eventually. And if the cannon were to blunt that attack, the guns would need ample case shot handy to apply in short order. Thus the order to conserve fire after the initial response to the Confederate fires. Instead of expending the less preferential case-shot in an attempt to disrupt, if not drive off, the Confederate gunners, better to save those four dozen rounds per gun anticipating a time when those would be of more practical use.

Keep in mind the numbers and this rough equation of combat power – specifically the time that combat power could be applied – was not lost on the rank and file. At least one battery on Cemetery Hill recognized the number of rounds left in their chests directly translated to the length of time they would be held in position under enemy fire. And they emptied chests in a less than soldierly manner… just leaving rounds on the ground. One officer later counted 48 rounds of 3-inch rounds laying on the ground where a limber had previously sat. Clearly the crew had run some numbers of their own and determined a better way to weather the storm.

We are getting rather far along here, as things will evolve. Yet still have not gotten to the other two questions. Let’s digest the matter offered thus far, and resume in the next post. The key point to keep in mind is the combat power of an artillery battery is in direct proportion to the number of ammunition chests in possession. Numbers… and type of projectile.. matter.

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