Category Archives: Mortars

3,180 shots at Fort Sumter between August 3 and 14, 1864: Third Major Bombardment continues

On August 16, 1864, Lieutenant-Colonel William Ames, Chief of Artillery of the Northern District (Morris and Folly Islands), Department of the South, provided an in progress report for the Third Major Bombardment of Fort Sumter.  The bombardment, which started on July 7, was at that time in its sixth week.  Ames provided this tally for the ordnance expended:

I have the honor to report the following number of projectiles and guns as expended in the bombardment of Fort Sumter from August 3 to August 14, inclusive: Three 200-pounder Parrott guns; 304 30-pounder Parrott shells, 299 100-pounder Parrott shells(*), 772 200-pounder Parrott shells, 13 300-pounder Parrott shells, 219 10-inch columbiad shells, 1,465 10-inch mortar shells, 108 13-inch mortar shells; total, 3,180.

The Third Major Bombardment had exceeded both previous “major” bombardments in terms of duration.  But it remained behind the Second Major Bombardment in terms of number of shots fired at Fort Sumter.  The problem facing the Federals was the amount of ordnance on hand – both guns and projectiles.  Already the Army was forced to borrow from the Navy.  And the Army lost three 200-pounder (8-inch) Parrotts during the first half of August.

The breakdown of rounds fired also illustrates some changes in the type of fires.  Recalling Ames’ reports from July 26 and August 1 for comparison, consider the proportions.  First from the period from July 7 to July 22:


More than half of the shots fired were from 100-pdr and 200-pdr Parrotts (that would be 6.4-inch and 8-inch for those who prefer the bore diameter designation… like me).  The mortars provided a quarter of the shots fired.  In the minorities were 30-pdr Parrotts, 300-pounder Parrotts, and the columbiads.

Then from July 23 to August 1:


The mortars increased in proportion to nearly a third.  The 30-pdr Parrotts provided a quarter of the rounds fired.  Triple the number of 300-pdr (I mean 10-inch) Parrotts.  Four times increase in the proportion of the columbiad contribution.  And decreasing noise from the 100-pdrs and 200-pdrs.

And from August 2 to August 14:


Now the mortars shouldered half the load.  The 200-pdrs fired nearly a quarter of the shots.  The columbiads sustained nearly the same ratio of shots fired.  But decreases from all the other Parrotts.  I’d love to see a breakdown of this on a day-by-day basis.  Furthermore, a similar breakdown, even if week-t0-week, for the other major bombardments would be interesting.

What these charts are demonstrating is the nature of the Third Major Bombardment. By the start of the second month of work, the Federals turned increasingly to vertical fires.  Some of the same reasons Federals at Petersburg brought up their mortars were at play.  Recall the Second Major Bombardment turned to mortars in the later part of November. However, the Third Major Bombardment of Fort Sumter was burning out resources faster than they could be replenished on Morris Island.

∗The “printed” official records indicate this as “200-pounder Parrott shells” but given the sequence and other information surrounding this report, I think that is a misprint and sh0uld read “100-pounder Parrott shells.”

(Citation from OR, Series I, Volume 35, Part II, Serial 66, page 241.)

Mortars and shells wanted at the front: Importance of horizontal fires at Petersburg

We often read the Petersburg siege demonstrated the emergence of “modern war” in some fashion.  The “coffee table book” history draws the the comparison between Virginia trenches of 1864-5 to French trenches of 1915-8.  There is some resemblance, but no more than any functional nature would derive.  Men can only dig a hole in the ground for protection in a finite number of combinations.  Nice surface comparison, but for the most part the trenches are not exactly a mountain of evidence for the “modern war” argument.

If looking to draw positive connections between Petersburg and the tactical nature of warfare in 1915-18, there are two aspects I suggest we examine – the increased use of vertical fires and  changed operational tempo.  That latter point – what we call OPTEMPO in modern parlance – I’ll save for a later post.  But I have mentioned vertical fires earlier this year in relation to the Overland Campaign… particularly Cold Harbor.  And of course, mortars were heavily employed to support the assault after the mine went off.  In the late summer of 1864, the mortars took on added importance at Petersburg. A series of correspondence on August 14, 1864 demonstrates this. That morning, Brigadier-General Henry Hunt wrote to his capable subordinate, Colonel Henry L. Abbot in charge of the siege artillery, directing mortars to the front:

Four 10-inch mortars with a proper supply of ammunition are wanted in the battery near the Taylor house to control a battery of 32-pounder rifles just beyond the crest, distance from 1,200 to 1,500 yards. It would be well to get them out to-day ready to move; they may be ordered into battery to-night. I will inform you then whether to send them. Please answer.

Hunt’s request was to meet a specific tactical need – silencing a Confederate battery that occupied a particularly troublesome position.  The answer to this problem was not direct, or horizontal fire.  Rather he proposed using heavy mortars to fire indirectly, or vertically, onto the Confederate position.  Abbot answered almost immediately that morning and set in motion actions to place the mortars that night. Abbot later suggested a specific position for the mortars, based on earlier experience along that line:

If the 10-inch mortars are ordered forward, I would earnestly request that they be put in the fourteen-gun battery where Pratt’s 4½-inch guns were. The range is essentially the same. The approach to this battery is very good, and to the old battery very bad, a matter of great importance in supplying 10-inch ammunition on account of its great weight; and, moreover, this battery is well made and the old battery very ill constructed, constantly caving under mortar fire.

 Looking back at Hunt’s map illustrating the artillery support during the Battle of the Crater, Pratt’s battery is indicated by the number “24” and circled in blue below:


The correspondence does not specify which Confederate battery was the target.  For the map above, I’ve highlighted one such battery, which would be “beyond the crest” and approximately 1,500 yards distant.  Notice the close proximity to the mine crater. The range cited was well within the capabilities of field pieces. The Confederate guns mentioned were indeed large caliber weapons.  But the Federals might have concentrated the fires of several batteries to damage the battery.  However, having read about the thousands of shells dumped on Fort Sumter, we must ask how long and at what cost would that be completed? 

There is no mention if Hunt required the use of 10-inch case shot from the mortars, as used during the Battle of the Crater.  That particular projectile, of experimental nature, would have done well to silence the Confederate battery while field pieces demolished the earthworks protecting the guns with direct fire. 

Concurrent with the correspondence with Hunt, Abbot also opened a request for more mortar ammunition… and not just a routine request… to Captain Theodore Edson, Ordnance Officer at Fort Monroe:

I am out of my supply of Coehorn mortar shells and the rebels are taking advantage of it. Please send me any shells and wooden plugs which you can possibly procure, on the mail boat, telegraphing me when they start. I don’t care for prepared ammunition. Time is very important.

Backig this up, Abbot further explained the pressing need for mortar ammunition to Brigadier-General George Ramsay, Army Chief of Ordnance in Washington and indicted this was a long standing request:

I have sixteen Coehorn mortars in position and not a shell in depot for them. The rebels keep up a constant mortar fire on us. I don’t care for prepared ammunition; all I want are shells, fuse-plugs, and paper fuses. These must be received very shortly or the army will suffer. I wrote on 15th ultimo, and telegraphed on 19th ultimo and 11th instant for a large supply. Please inform me at once whether I am to be supplied. Please also send 2,000 Parrott time-fuse plugs for siege guns.

The Confederates had also learned the value of vertical fire, and were now in position to employ some of the heavy mortars from Richmond along with some expedient weapons.  And at the same time, the Confederates were commencing production of their own Coehorn mortars.

Fast forward to 1917. When preparing the American Expeditionary Force for combat in France, American officers found themselves short of artillery in general.  But most acutely they called for howitzers and mortars capable of high angle fires.  Henry Abbot would have given them an “I told you!” look.  Vertical fires would become the dominant form of artillery support on the battlefield.

(Citations from OR, Series I, Volume 42, Part II, Serial 88, pages 182-3.)


Artillery support when the Petersburg mine went off

As you might guess, when thinking of the Crater at Petersburg, a subject which crosses my mind is the use of artillery in the operation.  Not to diminish the other aspects of the battle, but the artillery of the Army of the Potomac played an important role there… and is somewhat overlooked in my opinion.  I’m not an expert in the battle.  So I would direct you to one of many folks who have written book length treatments of the battle.

My schedule has prevented me from writing up more on Petersburg up to this time.  Likely, given the sesquicentennial pace, I’ll have to put that on my “after April 2015” stack.  But I did want to mention the artillery’s role and provide a graphic depiction, by way of Brigadier-General Henry Hunt’s map:


The map, and a busy map it is, includes a table breaking down by battery the type and number of guns engaged on July 30, 1864:


For those who are squinting, the roll call is eighteen 4-½-inch rifles, two 20-pdr Parrotts, fifty-two 3-inch rifles (3-inch Ordnance or 10-pdr Parrotts), thirty-eight 12-pdr Napoleons, ten 10-inch mortars, sixteen 8-inch mortars, and twenty-eight Coehorn mortars.  Grand total is 164 guns and mortars brought to bear on the Confederate lines in support of the assault.

Some of that number were in the 18th Corps sector and not firing directly in support of the assault.  Others were, likewise, firing on the 5th Corps front well to the south of the crater.  But all were firing at some time that morning to suppress or pin down the Confederates in conjunction with the assault.  For comparison, the “great bombardment” by the Confederates on July 3, 1863 during that “contest” at Gettysburg involved about 140 guns.

Hunt’s map indicates not only the battery positions, but also what the targets were.  This adds to the “clutter” on the map. But this is an incredible resource for determining his intent with respect to the fires placed upon the Confederate lines.


The snip above looks at the area of the mine, and just south.  Notice there are more dashed blue lines leading to the Confederate redoubt south of the mine than there are the redoubt above the mine.  Suppression of the Confederate line was the intent there.

Another Federal position worth noting is that of Company C, 1st Connecticut Heavy Artillery.  Battery number 8 on Hunt’s map contained ten 10-inch mortars.  Circled here in blue.


Those mortars fired on approximately 1,000 yards of the Confederate front, to the south of the crater (blue shading in the snip above).  Recall, these mortars were firing, for at least part of the day, case shot as constructed under Colonel Henry Abbot’s instructions.  Battery Number 19, Company B, 1st Connecticut, with six 4-½-inch rifles, located north-east (center-right on the snip above) of the mortars also covered a large section of the Confederate lines.

One problem with these arrangements is that suppressing fire requires a high rate of ammunition expenditure.  Suppressing fire cannot be sustained, even by a master artillery chief such as Hunt, for longer than a few hours.  At some point, fresh ammunition chests must be rotated in.  The assault had to quickly achieve the initial objectives, or lose the suppressing fire support.

Shrapnel from mortars: “far more effective than shell in… silencing batteries”

During the Civil War, as can be said for most of the “black powder” age, mortars usually fired one type of projectile – the shell.  There were a few variations, which were mostly incendiary shells.  The main disadvantage to the shell when fired vertically was the need to time the burst in order to achieve a desired effect.  A burst shell did scatter debris, but not in an even pattern.  Its main effect was the blast force, which was limited in area.  A “good” mortar shell burst a dozen feet or less above the intended target.  So at places like Fort Sumter or Petersburg, the practice of mortar fire with shells required the gunners to carefully estimate the time of flight;  translate that to the burn time of the fuse; and make the appropriate adjustments to the fuse, projectile, and weapon.  In the days of paper fuses and black powder, this was not an exact science.

With vertical fire, the force of gravity alone was often sufficient to kill or maim.  Such was the case with stone mortars.  But those weapons, as with shotguns, suffered from poor range.  What the mortar crews needed was some projectile which scattered sub-projectiles about the ground around the target area.  That in mind, some artillerists and ordnance men suggested the use of case-shot from mortars.  In the fall of 1863, then-Colonel Henry Abbot experimented with just such a projectile system at Washington, D.C.:

Knowing that a vertical fire of spherical case shot had been tried in Belgium with a view to dispensing with stone mortars, I applied early in 1863 to Major [James G.] Benton, commanding Washington arsenal, to prepare some projectiles for me in the usual manner, for experimental purposes.  He suggested that the expedient be tried of filling the 10-inch shell with 12-pounder canister shot and adding the bursting charge loose.  This I did in October, 1863; the first time, probably, that spherical case shot were ever fired from a mortar in this country.

The firing was at Fort Scott, in the defenses of Washington, south of the Potomac, the new model 10-inch siege mortar being used.  The target was in a valley fifty yards below the mortar and eight hundred and fifty yards distant.

I’d point out that remains of Fort Scott stand today in Arlington, Virginia, just west of Reagan National Airport.  The valley described was likely Four-Mile Run, south of the fort.

The projectile was the ordinary 10-inch mortar shell with twenty-seven of the balls of a 12-pounder canister (thirty-eight filled the shell) inserted through the fuze-hole, and a bursting charge of 2.5 pounds of powder added on top of them.  The shell weighted ninety pounds and each ball 0.43 pounds, making the total weight one hundred and four pounds.  A charge of one pound six ounces of mortar powder gave a range of eight hundred yards, with a time of flight of thirteen seconds.

For reference, the standard 10-inch mortar shell weighed 98 pounds when prepared for firing.  For the 10-inch Siege Mortar, Model 1861, the standard charge was four pounds of powder to propel out to a range of 2,235 yards.  Abbot used a smaller charge for the tests due to the shorter ranges required.  So one might postulate with a full service charge the case shot might have reached at least 2,000 yards also.

By placing observers at different stations to notice the points at which the shell was projected upon the distant hills, at its explosion, a close estimate of its height above the ground was secured.

Abbot included the results of ten test fires in a table:

Notice the dispersion of fragments reported, and the relation to the height of the burst.  As Abbot noted:

It was concluded from these experiments that when the shell burst, the balls fell in a cone about 30º at the vertex, while the fragments scattered very much more.  The balls had, at this range, ample force to kill, penetrating from three t0 seven inches into turf, where, when thrown by a man with his whole force, they entered less than one inch.  Indeed, a little computation will show that the velocity at impact must have exceeded two hundred feet per second, which, with a projectile weighing nearly half a pound, supplies ample living force to disable man or horse. Of course, if the range were very short the requisite velocity would not be acquired, as it depends essentially upon that of the shell at the instant of bursting.

The fact that the force of the bursting charge is expended in fracturing the shell, and does not materially scatter the balls contained in it, obviates for this kind of projectile the great cause of failure in mortar fire against troops, viz: that if the shell is burst over the point occupied by the enemy, the fragments scatter so widely as to render the position nearly a safe one, unless the shell is near the ground. The uncertainty of fuzes renders this height a matter of practical difficulty to control, especially as the fragments of such shells as bury themselves before exploding do no damage whatever.  The spherical case shot throws its balls evenly over a limited circular space, not exceeding in diameter its height above the ground at the instant of explosion, and hence must be far more effective than shell in retarding the progress of works of siege, or in silencing batteries.  It virtually extends the range of the stone mortar to that of the ordinary shell.

Here we have a “real” secret weapon from the Civil War.   But like all such evolutions, there were drawbacks.  Abbot does not provide the time to prepare the case shot compared to common shells.  Nor does he mention any special handling.  But no doubt the gunners would have been apprehensive about premature bursting of the case shot.  One exploding a few feet from the muzzle might wipe out a  an entire battery.

Silencing batteries?  Well in July 1864, there was a particular calling for such an ability.  And writing this account after the war Abbot mentioned that next:

In accordance with these views this projectile was employed in the battle of Petersburg mine, where General [Henry] Hunt’s orders for the artillery were to use every exertion to keep quiet the batteries of the enemy bearing upon the point of assault.

Yes, how did Hunt employ those 144 guns at the Crater?  A good question… and a good subject for another post!

(Citations from Henry L. Abbot, “Siege Artillery in the Campaigns Against Richmond with Notes on the 15-Inch Gun,” Professional Papers No. 14, Corps of Engineers, 1867, pages 25-7.)

June 4, 1864: Mortars to the front

Even though June 3, 1864 at Cold Harbor is best recalled as an infantryman’s fight, as mentioned yesterday, the Fifth Corps artillery launched over eighteen tons of ordnance towards the Confederate lines.  While massed batteries, as done with great effect just miles to the south at Malvern Hill in 1862, was not an applicable tactical option, the artillery remained an important combat force on the battlefield.  But field fortifications, even basic trenches, provided some mitigation against traditional field artillery.  With earth and wood protecting the soldiers from direct fire, the infantry could better withstand any eighteen tons of shot and shell the enemy might care to throw over.

Increasingly, not just in the Civil War but across the scope of warfare, vertical fires became more important where fortifications came into use.  In the Second Corps sector of the Federal lines, mid-day on June 3, Colonel John C. Tidball employed Coehorns in close proximity to the Confederate lines.  Captain James H. Wood, 4th New York Heavy Artillery, commanded the six mortars assigned to the Second Corps.  Wood wrote:

At 12 m. 3d of June one section (two pieces)was first placed in position at Cold Harbor, at a distance of about 800 yards from the rebel lines. The charge of powder used was 6 ounces and the length of fuse 15 seconds. The mortars were stationed in a hollow in rear of a belt of woods; 80 rounds were fired. It was reported by the front line of battle and the skirmishers of the Union forces that the shells made great havoc with the enemy, nearly every one exploding in their midst. At 7 p.m., by suggestion of General Barlow, the entire battery withdrew to the rear.

But the mortars would return.  That night the Federals completed mortar positions just 150 yards from the Confederate lines.  When the morning broke with heavy musketry, the mortars were ready:

At this place the charge of powder was 2 ½ ounces and the length of fuse 7 ½ and 8 seconds. The effect was excellent, and in about half an hour the rebels ceased to fire entirely. The position was such that the damage caused by the explosion of the shells was plainly discernible; and it was reported furthermore by our skirmishers that great execution ensued and the utmost consternation was visible among the enemy. The battery was highly complimented by Major-General Barlow and Brigadier-General Owen.

But their work soon attracted Confederate attention. Confederate field artillery fired in an attempt to damage or destroy the mortar battery.  But being so low and behind works, this did little good.  Confederate sharpshooters were more effective, preventing the gunners from standing up to aim or manage the mortars.  As a counter, the mortars began firing on the sharpshooters:

It was determined to try the effect of the mortar shells upon them and the whole battery delivered its fire, with the same charge of powder and length of fuse as at first. The result was almost instantaneous. Their firing was suppressed and was not resumed for several hours. It is perhaps not improper to observe that, during this affair, 2 rebels were seen to be blown 10 feet into the air, with heads detached. Their companions wildly scattered in every direction, and our infantry (General Owen’s brigade) giving a cheer, delivered a volley with telling effect.

Afterward the Confederates treated the mortars with caution.  Wood observed, “… that the enemy had fallen back in front of the mortars, leaving but a few skirmishers and sharpshooters in their front line of breast-works.”  In effect, the mortars had created a zone in which the Confederates could not operate.  While not a large zone, at least that offered some tactical advantage to the Federals.  But the Federals would need many more Coehorns if this was to be a useful advantage.

On the other side of the lines, the Confederates likewise started looking to vertical fires.  At that time, the Army of Northern Virginia lacked Coehorns.  But, Brigadier-General William N. Pendleton noted in his report on the campaign one adaptation of field artillery to the need.  “A 24-pounder howitzer of McIntosh’s battalion was adjusted a little in rear of the line and served as a mortar. It did good service in annoying the enemy’s working parties.”

Soon the howitzer and the Federal mortar began exchanging fires, as Wood recorded:

… the rebels fired at our forces with good range, using what was supposed to be a 24-pounder howitzer, trained as a mortar. The projectile thrown was spherical case-shot, by the explosion of one of which a man and a mortar were struck, but no serious damage was done to either. A new supply of ammunition having been received, it was decided to silence the rebel machine, if possible. By observing the smoke of their discharges, it was estimated that the distance was about 800 yards. A charge of 6 ounces of powder and a 15-second fuse were used, and after about one dozen discharges the enemy’s machine was silenced.

Wood’s mortars continued to do good work during the fighting at Cold Harbor.  The gunners had become very well practiced in the art of laying shells where needed.  Later, the mortars engaged in some more counter-battery fire, with good results:

On the 11th the remaining section, in charge of Captain Jones and Lieutenant Moore, was employed in firing at a rebel battery of light 12-pounders, which had opened upon a Union battery a short distance to our left. The mortars were estimated to be about 800 yards from the rebel battery. The charge was 5 ½ ounces and the length of fuse 15 seconds. The first shot struck on the left of the battery on a sand-bag breast-work, tearing a large hole therein. Another exploded inside the parapet, another in rear of the battery, another a short distance to the right. Assisted by the Union battery (light 12-pounders), the enemy’s guns were silenced. After this a few shells were thrown into a house almost in front of the mortars and 300 yards distant. The charge was 3 ½ ounces and the fuse 10 seconds in length. The house was a refuge for sharpshooters. One shell broke through the roof and exploded in the house. No more shots were observed to come from that locality.

With both armies remaining in close proximity for more than a week, the mortars were an idea weapon to use.  But there were precious few of them at the front.  Back in Massachusetts, Ames Manufacturing had a batch of fifty of the little mortars ready for inspection.  More Coehorns were on the way.

(Citations from OR, Series I, Volume 36, Part I, Serial 67, pages 527-8, 1050.)


“Light 12-pounders to be used as mortars”: A Spotsylvania ‘what if?’ from the artillery persepctive

I’m a bit behind on “coverage” of artillery subject on my planned sesquicentennial-themed time line.  So I hope you readers will indulge as I back-track here (and a few more times over the next few weeks), chronologically speaking.  The letter below properly fit into a post for the first week of May when I referred to the Army of the Potomac marching out of the Winter Encampment.  Among the last letters Brigadier-General Henry Hunt sent from his headquarters near Brandy Station was this message to Colonel Henry Abbot, 1st Connecticut Heavy Artillery and designated commander of the siege trains:

Artillery Headquarters, Army of the Potomac,
May 4, 1864.
Colonel Abbot:

My Dear Colonel: I have received your note of the 1st instant, and am glad to see things are progressing so favorably. I see you have as yet no Coehorns shipped, and that reminds me to ask you how many Coehorn mortars can be got. We will probably need all we can get. I have eight with me, and it would be well for the Ordnance Department to collect all they can. We move to-morrow; so you will soon hear from us in some shape, and will know about how soon the siege train will be required. Address as usual.
Truly, yours,
Henry J. Hunt,

Aside from the “My Dear Colonel,” this message doesn’t raise many eyebrows.  Though it is important to note that even on May 4, before a single shot was fired in the Overland Campaign, Hunt recognized the need for Coehorn mortars.  And he wanted a lot more than eight.  But we knew that already.

More interesting to us artillery-types is the postscript:

P. S.–Would it not be well for you to set apart a few men, with a good officer with some experimental practice with light 12-pounders to be used as mortars, i.e., try the ranges with different weights of powder, and see how the carriage will stand it, if necessary, to throw very heavy showers of shell in curved fire? I think that by digging a hole, and so lowering the trail–diminishing the charge–we will, at a pinch, be able to turn our light 12-pounders to very good account. Provision should be made, if the experiments prove satisfactory, to send on short notice a supply of 12-pounder shell. Can you send me, with your next letter to headquarters Army of the Potomac, a table of ranges for heavy rifled guns–30-pounder Parrotts and 4½ inch? I have none, and would like to have them about me; also a copy of heavy artillery.
Yours, truly,

Let me work this from the end back.  Hunt’s staff, having planned around the use of field pieces for the last year, now needed a refresher on heavy and siege weapons.  Hence the need for range tables for those heavy guns.

But the really interesting section is the request for trials using Napoleons as mortars.  For those less acquainted with Civil War artillery, the standard carriages used during the war allowed a dozen degrees of elevation, give or take depending on the gun and carriage.  For true vertical fires, the weapon must have at minimum 45º elevation.  The only way to achieve such elevation for a Civil War field gun on a standard carriage was, as Hunt suggested, to put the trail in a hole.  And since with the trail in such arrangement, the gun could not recoil, the firing charge had to be reduced lest the force destroy the carriage.

You might ask, what advantage might be gained by firing at such high angles?  A tactical advantage.  With more elaborate field fortifications appearing on the battlefield, the horizontal fires of conventional field guns, and even to an extent howitzers, was at a disadvantage.  Both sides built up heavy front works – higher parapets made of heaped earth and logs.  The penetrating power of direct fire artillery – even the rifles – was not sufficient to break such barriers without a prolonged bombardment.  But vertical fire,  such as from a mortar, could place a shell beyond those works, and do great damage to the defenders.

So how did those trials go?  Three days later Abbot sent this update:

Fort Richardson, VA., May 7, 1864.
Brig. Gen. H. J. Hunt,
Chief of Artillery, Army of the Potomac:

General: Yours of 4th instant is received. There are only five Coehorns now at arsenal, but the rest are expected very soon, and fifty have been ordered with all possible speed. I have ordered experiments with the light 12-pounder gun as a mortar to-day, and will report results as soon as obtained. The Ordnance Department has an abundant supply of ammunition for them on hand. I send by this mail a copy of heavy artillery, which contains an addition to the old range table prepared by General Barry, giving the best rifle ranges known to me; also a similar table prepared by Captain Treadwell, Ordnance Department. I inclose a table of experiments on the new-model 10-inch mortar, to show the difference between the Gomer and elliptical chamber; also a copy of a report of some experiments with spherical case from a 10-inch mortar, which are so successful that I have ordered a large supply of 12-pounder spherical case balls for our train. I also think of taking two 12-pounder Whitworths along. They make elegant sharpshooting to dismount guns. They are very light, and may be of service for such special uses. The following is the present condition of my train afloat: 4½-inch–18 guns. 20 carriages, 20 implements, 20 platforms, 6,520 rounds; 30-pounders–10 guns, 20 carriages, 10 implements, 20 platforms, 5,025 rounds; 10-inch mortars–10 guns, 10 carriages, 10 implements, 10 platforms, 2,000 projectiles; 8-inch mortars–20 guns, 9 carriages, 20 implements, 2,600 projectiles; 8-inch siege howitzers–10 guns, 4 carriages; Coehorns–3,796 projectiles; 100-pounders–6 guns, 6 carriages, 1,400 projectiles; 1,250 barrels powder, 1 battery wagon, 1 forge, 4 sling carts.

Very respectfully, your obedient servant,
Henry L. Abbot,  Colonel First Connecticut Artillery.

Only five more Coehorns?  I should mention Brigadier-General Albion P. Howe’s report on the Washington Defenses from May 17 tallied over twenty Coehorns in the forts.  As indicated in Abbot’s letter, the desired range tables and a lot more information went forward to Hunt.  (Two other interesting topics here – the 12-pdr Whitworths and the 10-inch mortar case shot – I will save for later posts.  The latter becomes important at Petersburg, particularly in the Battle of the Crater.)

But he had not gotten around to trials of the Napoleons as mortars.  Nor would he.  Two days later Abbot received orders to move his force to the Bermuda Hundred and join Major-General Benjamin Butler’s force.  At that point, Abbot’s attention was to operations at the front and not ordnance experiments. UPDATE:  Abbot wasn’t able to test, but his subordinates were.  See this post.

However, consider this “what if?”  Going into the Overland Campaign, the Army of the Potomac had over 100 Napoleon guns.  What if the requested experiments had gone on earlier in the winter, with a proper and refined employment method, to include range tables, been derived?

Now… what if the assault on the Bloody Angle has been initiated by 25 or 50 or even 100 Napoleons firing shells at high angles into the Confederate works, instead of just eight Coehorns?  Granted, as the employment of the Coehors on May 12, 1864 demonstrated, poor accuracy of vertical fires in the black powder era argued against its use in close proximity to friendly forces.  But a preparatory bombardment to open the way for an infantry assault was possible. Similar bombardments supported assaults on entrenchments over fifty years later during World War I.  And for good measure, unlike 1917’s trenches, the Confederates at Spotsylvania had no prepared overhead cover.

(Citations from OR, Series I, Volume 36, Part II, Serial 68, pages 373, 484-5.)

“The Coehorn mortars were employed wherever circumstances would permit”: Mortars at Spotsylvania

When the Army of the Potomac broke winter quarters in early May 1864, the Artillery Reserve brought along a somewhat novel weapon – 24-pdr Coehorn mortars.

Seven Days 26 May 12 170

Eight of these mortars, with 100 shells each, traveled with the reserve park, manned by Company E, 15th New York Heavy Artillery.  Of their performance and utilization, Brigadier-General Henry Hunt provided a single sentence in a section of his report on the Battle of Spotsylvania Court House:  “From the 8th to the 16th the Coehorn mortars were employed wherever circumstances would permit of their use, and always with good results…”  The results were so good, in fact, that by June, every corps in the army received their own allotment of Coehorns.

As I mentioned in an earlier post, Hunt saw these light mortars as a means to provide fire support in a particular niche not served by the normal field guns (and for which he did not think howitzers could provide).  Recall the Coehorns had provided remarkable support during the siege on Morris Island the previous summer.  And were requested, but not provided, for the siege at Vicksburg – where ersatz wooden mortars filled in.

That niche, defined, was to lay explosive projectiles on a position shielded from direct line of sight, and thus fire.  Such a tactical requirement was seldom of great importance in a pitch battle, with maneuvering forces.  But where the armies sat in close proximity for days on end, and fortifications grew up to protect those forces, the mortar’s high angle fire was of great importance.  So 150 years ago today, with the armies tangled in a series of entrenchments in Spotsylvania County, those eight Coehorns were arguably more useful than a couple batteries of 3-inch rifles.

There was one other suggestion for vertical fire made by Hunt prior to the campaign which might rank as novel… or perhaps even bizarre.  I’ll take a look at that in a later post.  But as a teaser, think a “gun-howitzer-mortar.”

(Citation from OR, Series I, Volume 36, Part I, Serial 67, page 286.)