Dahlgren on Shrapnel, part 2: “these results are only to be considered as general terms”

As discussed earlier, while working on a system of boat howitzers to equip the US Navy, John Dahlgren conducted a detailed study of the behavior of shrapnel.  He identified three factors which governed the performance of shrapnel, from a target point of view, and thus would provide the requirements for the practice of fire for such projectiles.  Those were the range, the time of projectile flight, and height of burst above the ground. And those were the same requirements we saw in the illustration from other pre-war manuals.


What Dahlgren’s study offered was a “schooled” approach to the problem, as he felt the behavior should be scientifically defined to provide a reliable reference to the gunner.  Dahlgren determined shrapnel was most effective when exploding 50 to 130 yards in front of and 4 to 15 feet above the intended target.  So the next question – how to make a shrapnel projectile’s burst to occur with such regularity that the gunner could achieve a result within that “most effective” space.  The key to achieving such results would be accurately setting the burn time of the fuse.

But that was easier said than done, as Dahlgren observed:

The shrapnel fired from cannon may have a velocity in the different parts of its trajectory, amounting to as much as 1200 or 1500 feet per second, and hence a difference in the burning of the fuze, almost inappreciable in time, will be made very perceptible by the variations in the distances at which the explosion occurs; thus, with the 1200 feet per second, a fourth of a second will produce an error of 100 yards:  if the velocity be 600 feet per second, the difference in distance will still be fifty yards.

Keep in mind at the time of writing, most services used paper fuses.  In the use of such, the length of the paper was cut, using a rule calibrated to the burn rate of the fuse, for the desired burn time.  The Bormann fuse was just coming into use.  But in either case (and the case for most of the other types in use) the smallest time measure provided was the quarter second.  What Dahlgren was telling us is that quarter second could produce an error of between 50 to 100 yards.  In other words, this would produce an unacceptable variation which might serve to throw shrapnel completely outside the optimal window, if not the marginally effective zone.

Dalgren went on to point out another factor, which fell outside the gunner’s control, was the consistency of fuses.  Regularity in burn rate was a problem at the time.  Furthermore, the set of the fuse would often change the performance, in some cases leading to misfires and other problems.  So the bottom line this was not simply a case of selecting a fuse length and firing the shrapnel.  More thought was required.

Dahlgren did point out that British practice was to provide each shrapnel with four fuses.  These were defined by the ranges allowed based on the fuse burn time – 650 yards, 900 yards, and 1100 yards, with a fourth left to be cut based on tactical needs.  Not specifically stated, but assumed, is these allowed the gunner select a fuse based on where he wanted the shrapnel balls to hit the ground.  In other words, the 650 yard fuse would cause a burst at around 500 yards, with balls proceeding forward another 150 yards.. .give or take.

Though Dahglren spent some time describing the nature and functionality of various fuses available at the time, he shorted the discussion with a “might be too much elaborate this brief sketch” … so allow me to follow that lead at time time.  He simply noted that in US service (both land and sea) the standard was to provide shrapnel with fuses pre-configured for 1, 2, 3, 4, and 5 seconds (color coded).  It was not desirable to modify those fuses in order to shave off fractions of a second. And while he provided for some modifications or fabrications, those were considered impractical for field service.  Instead, the focus should be, he felt, on precise employment of the standard fuses (again, not only burn time but placement in the projectile to reduce the chance of misfire, failure to fire, or other derived irregularities).

What this leads us to is a somewhat fixed practice of fire.  A gunner would seek to fire shrapnel when the target was at a range which matched to the burn time of those configured fuses.  Granted, that might be inconvenient as battles are too often fought at odd ranges (you know… were four map sheets join and all).  But this plays upon that 50 to 130 yard fall of the balls after the shrapnel burst.  To be blunt, this was horseshoes and hand-grenades work.  So long as the time of burn was within that desired  50 to 130 yard, an effect could be felt.

Now the critical point fell upon the sighting arrangements of the cannon.  Given that fuses were working on a “set” time, and from that the gunner derived the zone in which the balls would fall, he had to work back to ensuring the gun tube was properly oriented to push the projectile on the desired flight path.  Azimuth… the easier part of that problem.  Elevation was the question mark.  Dahlgren explained the functioning of the fuse and elevation as such:

… the elevation is given to the piece which is required to carry the projectile to the proper distance, while the fuze adjusts the explosion to the time which the projectile occupies in traversing this space.

Given those fixed fuses, Dahlgren suggested the British method would work best for sights:

The sight in this method is graduated to the intervals of time which will carry the projectile to its desired position; and each graduation is accompanied by the two distances which include the spread of shrapnel balls.

Thus if the fuze be adjusted to 2″, and the piece elevated by the sight, raised to the line on it marked 2″, then the shrapnel will burst about 500 yards from the piece, and spread its balls from that point a considerable distance farther – effectively, at least 150 yards.

Note here the use of the symbol (“) for seconds, as opposed to referencing inches.  Select a measured fuse to fire at a measured distance and use a set elevation on the sight.  The gunner was to trust the equipment and ordnance provided to perform with regularity.  No need to know the science here.  Just basic rules of thumb – target at 650 yards, select a two second fuse, elevate gun to the two second mark on the sight.  Fire.

Dahlgren admitted that the factors necessary (range to burst, elevations, etc.) for this arrangement needed refinement, agreeing his department needed to work out those details.  Still, he concluded:

Even when obtained, these results are only to be considered as general terms that are to guide the intelligent officer to a proper application of shrapnel or of shells, when used upon uncovered troops; there being left in the fractions of seconds, a wide margin for the tact and discretion that are to make his fire more or less effectual.

A bureaucratic way of saying, “We’ll get the gunner in the ballpark, but someone still needs to observe fires in order to hit the target.”

We can actually trace Dahlgren’s practice of fire directly into the manuals.  From The Ordnance Instructions for the United States Navy of 1860, we have this paragraph regarding shrapnel from boat howitzers:

Similar terms are used in marking the sight and the fuze.  Thus, if the fuze be adjusted to 2″, and the piece elevated by the sight raised to the line on it marked 2″, then the shrapnel will burst about 500 yards from the piece and spread its balls from that point to a considerable distance farther – effectively at least 150 yards.

So by 1860, the observation became the rule. A “practice of fire” described in one paragraph.

However.. you know there was going to be a “but… ” here…. There is a problem with this practice of fire.  Aside from that paragraph in the Instructions, there is no table in that manual detailing the particulars for three second, four second, or five second settings. Now there was a separate set of manuals detailing how the Navy wanted sailors to use boat howitzers.  And there we find this table (The Naval Howitzer Ashore, 1865):


This is “good stuff” but not the raw inputs needed for the “practice of fire” for shrapnel.  We don’t find table increments for seconds as defined on the sight.  Instead we have degrees of elevation, with ranges and time of flight provided.  But notice this is broken down, were available, for shrapnel and shell.  While not directly supporting the “practice of fire” we can see how the figures given in the practice play out.

Turning again to the two second time of flight, we see a close approximation at 1.9 seconds associated with a range of 500 yards for shrapnel from a 12-pdr smoothbore howitzer (the caliber and type Dahglren cited in his tests).  That occurs with a 1º elevation.

Notice if we go down a line to the particulars for shells, the two second time of flight would fall somewhere between 516 yards and 730 yards, likely around the midpoint between those two.  With an elevation between 1º and 2º.This requires some bending of the mind around the ballistics, but I submit the ranges given for shrapnel coincide with the range where the burst occurs, not where the balls would fall.  However, that given for the shell is where the projectile hits ground (and the gunner wants it to explode).  Thus, I’d submit we are reading different definitions for “range” on those lines accounting for the different uses of projectile types.

That “but….” presented within this table lingers over the “practice of fire” like a cloud in battle obscuring the target.  Yes, Dahlgren defined the practice in clear terms before the war.  And yes, those practices were incorporated in the pre-war (1860) manual.  However, at least by 1865, the tables provided failed to give the gunner such “tolerable approximations” that Dahlgren sought in 1852.  One gets the impression that shrapnel was just not that important after all!

(Citations from John A. Dahlgren, A System of Boat Armament in the United States Navy, Philadelphia: A. Hart, 1852, pages 56, 69-70; Ordnance Instructions for the United States Navy, Washington: George W. Bowman, 1860, page 109.)


May 4, 1865: “The rebel ram Stonewall” on the loose

On May 4, 1865, Rear-Admiral John Dahlgren forwarded a copy of orders, posted the previous day to the South Atlantic Blockading Squadron, to Major-General Quincy Gillmore.  The copy was in part a courtesy to the Army commander, to let him know of the Navy’s operational matters.  But at the same time was a warning that despite the surrender of Confederate forces, there were many loose ends left untied… and one of those was a rather important, advanced warship sailing on the high seas – the CSS Stonewall.

The Stonewall was an advanced vessel for her time.  And she entered the stage from a backdrop of intrigue and secrecy… of the type novelists love to use.  The ship was laid down at Bordeaux, France in 1863.  Designed by Lucien Arman as an ocean-going ironclad, the Stonewall boasted a 4 ½ inch armor belt along the waterline and a 5 ½ armored pilot’s compartment.  Her offensive power was one 300-pdr (10-inch) and two 150-pdr (8-inch) Armstrong rifles (and there is some indication that at least one 70-pdr (6.4-inch) rifle was also on board when she sailed from Europe).  Add to that firepower the “ram bow” for use in close combat.  And to make that ram even more useful, the Stonewall featured twin screws and rudders, affording greater maneuverability than most vessels of her time.

The Stonewall was one of five “blue water” ironclads ordered from European shipyards by Confederate agents. Two “Laird Rams” were built in England under the cover of an Egyptian customer name.  But those were seized by the British government in the fall of 1863 and then served for the Royal Navy as coast defense vessels.  An armored frigate named Santa Maria, with an impressive twelve 8-inch rifles, was started in the yards of J.L. Thompson and Sons in 1863.  But once the true nature of the work was discovered, the Santa Maria became the Danish Danmark.

In France, Confederate agents contracted for the Stonewall and a sister ship under the cover names Sphinx and Cheops, respectively.  Despite the legal setbacks in England, the work in France continued into 1864.  The intrigue pitted the French Emperor, Napoleon III, against his own government in an effort to see the vessels delivered to the Confederates.  But that was foiled by a leak of information to the US consulate.  As result, the Sphinx was sold to Denmark as the Stærkodder, and her incomplete sister ship to Prussia as the SMS Prinz Adalbert.  Though the Stærkodder received a Danish crew, the shipbuilder and the Danes failed to finalize the deal.  In the confusion, Arman completed a deal with the Confederates.  On January 6, 1865, a Confederate crew went on board the ironclad then in Copenhagen.

With several US cruisers keeping pace, the Stonewall went to sea only to spring a leak and seek a Spanish port.  After repairs, Captain T.J. Page took the Stonewall to sea, only to watch the Federal cruisers run off instead of offering battle.  Page then put in to Lisbon for provisions and fuel in preparation for a trans-Atlantic run.  Not until late April was she ready for sea.  But when she put to sea, the Federals still lacked a vessel capable of intercepting and engaging the Stonewall.  So she posed a significant threat on the high seas during the opening days of May, 1865.

Dahlgren’s copy of General Orders No. 48, forwarded to Gillmore, carried this cover:

General: I am informed by the Navy Department that the rebel ram Stonewall has left Teneriffe, and “her destination is believed to be some point on our coast.” Several vessels of the squadron are cruising along this coast and other orders have been issued.

The referenced orders included notices from the Navy Department, which not only called attention to the movements of the Stonewall, but also the flight of President Jefferson F. Davis. The two seemed connected at the time.  And was not far out of the question for Davis to flee to Cuba using the Stonewall as some executive escape vessel.  Dahlgren’s standing orders were:

The commanders of vessels stationed along the coast will use every means in their power to communicate to the iron-clads at Port Royal and Charleston the earliest intelligence of any vessel approaching the coast resembling the Stonewall, and to prevent the escape of the rebel leader and his accomplices. It is difficult to fix upon any precise point where this vessel might be expected; but once seen every effort should be made to spread the information among the squadron, and to bring the monitors within range of her, particularly to keep sight of her, so as to retain a knowledge of her locality. The Canonicus and Nantucket are at Port Royal: the Passaic and Catskill at Charleston.

At the same time 150 years ago, the Stonewall was nearing Nassau.  She would reach that port on May 6.  Unsure of the situation, Page would then make for Havana, Cuba.  There word of the Confederate surrenders caught up with the Stonewall.  Page opted to “sell” his vessel to Spanish authorities there.  Weeks later, US officials purchased the Stonewall from the Spanish and sailed her to the Washington Navy Yard.  There she studied in detail but generally found to be unsuitable to the needs of the post-war navy. But this did allow for some interesting photos with the Stonewall anchored near some of the Federal monitors for comparison.

The Stonewall‘s mission, when the Confederates first took possession of the ship, was to break the blockade.  She might have raided Port Royal and disrupted the South Atlantic Blockading Squadron.  Had she arrived in late January, Page might have even stalled Sherman’s march through South Carolina for a while.  But by itself, the Stonewall was simply not enough to do more than play the fly to the Federal elephant’s advance.  She might have made headlines, but could not have done anything substantial  (as by that time the Confederates had no ports to open!).  As events unfolded, the legal and logistic snags ensured the Stonewall was late even for that minor role.

But the “What if” question remains for us to play around with.  Was the Stonewall, on paper a superior ship to the monitors, a potential game changer?  Well, speaking to the negative of that question, her sister ship in Prussian service was found to leak badly and was deemed a poor handling ship on the seaways.  The Prussians refitted the ship, adding better structures, armor, and Krupp cannons.  Still she was destined to play no role in two wars (Austro-Prussian and Franco-Prussian) fought during her service period.  The Prinz Adalbert was broken up in 1878.

However, on the positive side of that question, the Stonewall herself went on to a successful career, of sorts, under a different flag in a different kind of civil war.  In 1867, the Stonewall was sold to the Tokugawa Shogunate (for a substantial profit, by the way) and sent off for Japan.  Before arriving, the Shogunate lost ground and the Americans took control of the vessel when it arrived in Yokahama (April 24, 1868).   A deal with the Meiji government delivered the ironclad, then renamed Kōtetsu.  Over the following years, the Kōtetsu fought in several engagements as part of the Boshin War between Shogunate and the Imperial Court.   The most important of which was the battle of Hakodate in May 1869 (but four years removed from her last Confederate days).

There, the Kōtetsu dominated a force of unarmored ships.  That episode might provide some insight into what “might have been” at Port Royal.  Though the Kōtetsu appears to have remained in the coastal waters of Japan throughout these operations, never testing her ability to fight on ocean waters.

The French built ex-Danish, ex-Confederate, ex-American, ex-Shogunate Japanese ironclad was renamed Azuma in 1871 and rated coast-defense battleship.  She was finally stricken in 1888 and used as an accommodation hulk.  But, looking many decades into the future at that time, the former CSS Stonewall was the first rated “battleship” used by the Imperial Japanese Navy.  Many decades later the Azuma‘s descendants would contest an ocean with the descendants of the American monitors, in some of history’s largest naval battles.

(Citation from OR, Series I, Volume 47, Part III, Serial 100, pages 299-300.)

“The light-infantry drill will be best adapted to this service”: Dahlgren’s instructions for landing parties

Earlier this week, I mentioned the work of Navy landing parties in raids along the Georgia coast 150 years ago.  In the same time line, 150 years ago, Rear-Admiral John Dahlgren saw the need to formalize the equipment, organization, and drill of the sailors involved with these landing parties.  On August 8, 1864 he sent around orders addressing the subject:

Boat artillery and infantry, South Atlantic Blockading Squadron.

It has frequently happened that the peculiar nature of the duties in this command has required the service of bodies of men to be landed from vessels to act for a short time as infantry, assisted by light fieldpieces.

In order to meet similar exigencies commanders of vessels will take pains to select from their crews such men as may seem to have a turn for this kind of duty and have them drilled with small arms until they have attained the necessary proficiency.

In so doing it is to be borne in mind that the drill and maneuverings are to be few and exceedingly simple.

The men should be thoroughly skilled in the loading and firing of their weapon, and the firing at a mark is to be encouraged.

The light-infantry drill will be best adapted to this service, and to the habits of seamen.

The preferable arm, when it can be had, will be the new navy rifled musket, known as the Plymouth musket, because the first of this kind were made for the U.S. ship Plymouth when under my command, the pattern of which was got up by myself as most suitable for sea service.

It is a short musket, about 34 inches in the barrel, bore 0.69 inch., and rifled.

Its special bayonet is a short, broad, and stout knife, of the well-known Bowie pattern, the principle use of which I designed to be in the hand in close conflict, such as boarding.  In campaigning it would also serve many wants; but it may be fixed and used as a bayonet.

There is also a sword bayonet similar to that of the French, making the total length of the weapon, from butt to point, about equal to that of the army musket with ordinary bayonet.

The musket Dahlgren describes was also known as the Whitney Model 1861, seen here with the sword bayonet:

Click the image above to see a detailed examination of the weapon on the Civil War Relicman’s site. More views may be seen on the National Firearms Museum website.  Notice that Dahlgren preferred this weapon over the Spencer repeater, despite the later’s performance in earlier engagements… and even though Dahlgren had approved of the weapon in tests at the Navy Yard.

Dahlgren went on to praise this weapon as “perfectly balanced” when the bayonet is not fixed.  He then touched upon the ammunition used, suggesting buckshot for use at short range (not buck-and-ball, mind you).  “As a general rule we have too much neglected the use of this formidable ammunition for small arms.”  Lastly on the subject of small arms, he added, “the men should be landed occasionally for practice, especially as skirmishers.”  Again, the intent to match the Army’s light infantry drill where possible.

On the subject of artillery, Dahlgren wrote:

The artillery is to consist of the boat howitzer, light and heavy 12-pounder, rifled and smooth.

These are to be organized in sections of two, with three sections to a battery, consisting of four smooth and two rifled 12-pounders.

This, however, is designed rather as a matter of administrative organization to regulate the proportions of rifled guns and for supplies of ammunition, spare parts, etc.

I desire particularly to disabuse the naval mind of the idea which prevails as to the proper use of boat light artillery.

In designing these pieces, I never intended that they should be assembled in masses, just the contrary, as every effort has been made to simplify the peice itself so that but little practice is required to understand its manual and to use it, so it was intended to avoid the complication of them produced by combination in masses, as practice in the land service.

The boat howitzer and its field carriage is so light that it can be drawn by its crew when no other artillery can be taken, over broken ground, among woods, up steep ascents, seeking cover where a tree or a bush, ditch, or dwelling offers it.  The ammunition is carried in pouches, so that no obstacle exists on this account.

And thus, from unexpected positions, difficult of access and scattered in many directions, the navy howitzers, while dispersed, and therefore less exposed to the enemy’s guns, may concentrate or divide their own fire as may be best.

In other words, the piece is designed to bear the relation to other artillery as the light infantry does to infantry of the line.

Great analogy directly from the man who designed the weapon.

Dahlgren went on to point out the artillery crews would not carry any small arms, but only have Bowie knives for their close defense…

… and when unable to retain possession of the piece, disable it by carrying away the fighting bolt, without which the gun cannot be fired, and which is so nice of adjustment that it can only be supplied from the machine shop, and there is no substitute for it.

There was a higher purpose for Dahlgren’s orders, and he did not shy away from its mention:

The published Instructions for the Naval Academy, and the habit, so far as it has come under my observation, have been to organize and maneuver in masses, as customary in the land service with light and heavy artillery.

I have never had the means before this to give this branch of the service its proper form.  Now I am enabled to make the effort by the receipt of a number of howitzers and Plymouth muskets, with Bowie knives, etc.

But the personnel is wanted, as a preparatory step I desire that commanders will select their men and drill them to their muskets, and to the howitzer if they have them.

Dahlgren was stepping back into his familiar role of weapons development.  In this case, refining the tactics used in the employment of the weapons.  He was indeed trying to prove his assertions about tactics correct.

(Citations from ORN, Series I, Volume 15, pages 622-4.)