Category Archives: Engineers

Pioneers for the Overland Campaign

Issued on April 5, 1864, General Orders No. 15 from Headquarters, Army of the Potomac amended the organization of the provost-marshal’s department, the transportation allotments, and the organization of pioneer details.  Paragraph II of the order dealt with the latter subject:

II. The following is established as the organization and equipment of the pioneer parties of this army:

First. The unit of organization will be by brigade. In each brigade 1 man shall be selected for every 50 men equipped for duty in it; for every 10 men thus selected a corporal shall be detailed, and for every 20 a sergeant, and for each brigade 1 lieutenant.

For each division a first lieutenant of old date or a captain shall be detailed to command the pioneers of the division, who will be a member of the division staff, and be furnished with a horse and equipments by the quartermaster’s department.

The pioneers will be armed as they were in their regiments, and men and officers will be especially selected for fitness for the duty. They will be excused from all guard and picket duty and from ordinary fatigue details. The tools will be furnished in the following proportions, viz, five-tenths axes, three-tenths shovels, two-tenths picks, and be carried on pack-mules during the march, each mule carrying the tools for 40 pioneers. The quartermaster’s department will provide the necessary mules and appropriate panniers for this service.

Brigade and division commanders are directed to give special attention to the prompt formation and equipment of their pioneer parties.

In camp, the pioneer parties will make the ordinary repairs to roads, build bridges, &c. On the march, they will move at the head of the infantry column and promptly put in order all parts of the route where artillery and wagons have to pass, whether for their own command or for troops to follow.

Second. Corps commanders will cause 1 non-commissioned officer and 25 efficient men to be selected and placed under the orders of the chief quartermaster of the corps to serve as a mounted pioneer party to accompany the trains, and to be provided with 10 axes, 10 spades, and 5 picks. The horses and equipments for the pioneers for the trains will be furnished by the quartermaster’s department.

The Army of the Potomac, and other field armies, used pioneer details throughout the war.  This order established two “pools” of engineers – one supporting the maneuver elements and another for the corps trains.

And what was the mission assigned those pioneers?  Building roads and bridges.  There is a common interpretation that by 1864 tactical combat evolved into a entrenchment-dominated, semi-static infantry firefight.  But, the shovel, pick, and axe were also tools to enable maneuver both to the battlefield and upon it.  See, the Overland Campaign was far more than a series of frontal assaults and ever extending trench lines.

(Citation from OR, Series I, Volume 33, Serial 60, page 805.)

Henry Benham, pontoons, and a lot of photos: What the engineers did over the winter

On January 25, 1864, Brigadier-General Henry W. Benham, commanding the Engineer Brigade of the Army of the Potomac, completed a lengthy report for Brigadier-General Joseph G. Totten, the Chief Engineer of the US Army.  The report touched upon several subjects, but largely concentrated on improvements to bridging techniques then in use. This was not a new round of correspondence.  Benham wrote a similarly lengthy and detailed letter to Totten in November 1863, discussing changes in the drill for pontoon bridging.

The reports, including enclosures from subordinate officers, include over fifteen pages total in the printed OR.  Far too much for a single blog post.  So I might examine in fine detail at another date.  Feel free to browse the November 1863 letter or the January 1864 report if I don’t get to that examination in short order.  I suspect a detailed examination would elicit a long sigh at the discussion anchor bolts, abutment sills, and claw-balks.  So let me focus on something less “engineer-y” and perhaps a bit into the historiography side of things.  At the end of his November letter, Benham mentioned some photographs sent along with the correspondence:

I have the pleasure of inclosing you, for the further explanation of the method of laying these bridges, some photographic views taken during the progress of construction.

No. 1 shows the pontoons ready with the material, and the boat squads ready for the construction (at foot of East Fifteenth street).

No. 2 shows the progress of construction of the raft after four to five minutes’ labor.

No. 3 shows the progress of the bridge raft after six to seven minutes’ labor.

No. 4 shows the bridge completed, with the bridge squads formed ready to march off. Parts of a trestle and canvas pontoon bridge across a cove along the shore are in view here.

No. 5 shows, from a nearer point of view, the pontoon bridge ready for service.

No. 6 gives the view down the Eastern Branch with pontoon bridge to beyond Navy-Yard Bridge, and oarsmen having oars raised ready to move the bridge for dismantling. Parts of pontoon balk-head used for laying the bridge raft are shown in foreground as it was placed to save the men from the water, though rather delaying than expediting the work. (emphasis added)

Believing that they would also be interesting at the Department, I have also added two other photographic views.

No. 7, showing the old or generally practiced method of laying bridges by successive pontoons.

No. 8, a view of the pontoon bridges laid by the engineer brigade under my command on the morning of April 29, 1863, at Franklin’s Crossing, 2½ miles below Fredericksburg. This shows in the distance the ruins of the villa of Mansfield, the site of General Bayard’s death.

Photo “No. 8″ referenced by Benham may be one of those examined by John Hennessy and Eric Mink in 2011.   Of the others described (or is it “captioned”) by Benham, I’ve found no direct matches.  However this photo from the Library of Congress collection is a close match to “No. 6″:

This shows two pontoon bridges across the Anacostia River, looking from the Navy Yard.  Lots of neat stuff to discuss in this photo.  But for today, let’s just consider this as establishing Benham’s practice of using photographs to support his suggestion (and I bet Benham would have loved PowerPoint!).

That in mind, consider a section from the January 25, 1864 report:

The modification I propose (of which I inclose sketch) in the French pontoon is to take off 3 feet in length from the bow and 2 feet from the stern, while the “floor” remains of the same length, the ends to the depth of one plank downward to be of a thick plank or timber, with a shield or bunter which should slope about 3 inches outward.

Benham went on to say this modification would prevent some of the damage to the pontoons while on the march and make handling much easier.  Here’s the line drawing included with the report:


Fairly typical comparison diagram, using dotted lines to demonstrate the differences between the original and proposed modification.  Probably sufficient to demonstrate the particulars for an engineer of Totten’s experience.  But what do they say – “A picture is worth a thousand words”?  How about this picture, might it offer a thousand words comparing two types of pontoons?

Notice the difference between these two pontoons, particularly at the bow end.  While not precisely matching the dashed lines in Benham’s drawing, the pontoon on the right is close to his proposed modification.  Was this a photograph taken for the benefit of Benhan to demonstrate his suggested changes?

Working against my suggestion, the Library of Congress record for this photo does not provide a location.  The original caption on the back of the stero-view card does not mention any special nature of the two boats:

This view shows two of the boats (of which the army bridge is made) on wheels ready for the march.  Each pontoon wagon is drawn by six mules.  These pontoons were always getting stuck in the mud, and the soldiers, struggling along under their own burdens, were obliged to haul on the drag ropes, and raise the blockade.  Probably no soldier will see this view without being reminded of the time when he helped to pull these pontoons out of the mud, and comforted himself by searing at the mules.

Doesn’t sound as if this photograph captured a comparison of two type of pontoons. Maybe the studio felt the public would not appreciate the comparison, and thus offered a “pedestrian” caption.

However there are several other views of pontoons dated to the winter of 1864, taken at the Engineer Brigade camp at Rappahannock Station.  And some seem ready made for a comparison of the two types.  This photo carries the Library of Congress caption “Pontoon wagon and boat, 50th New York Engineers, Rappahannock (i.e. Brandy) Station, Va., March, (i.e. Feb.) 1864.”:

So the right time and place.  And this appears to be a standard “French Pontoon.”

Compare to this photo, also citing the 50th New York Engineer camp at Rappahannock Station in March 1864:

If not an exact match for Benham’s drawing, it does look like the pontoon on the right side of the photo above.  And another photo must have captured the same (or similar) boat from the front:

With more of these in the background… see them?

There’s even a photograph of a wagon without the pontoon:

And let’s not forget the canvas pontoon:

That photo, in particular, just stands out as if tailor made for illustrating some manual.  The men are in the background, not the foreground.  The subject here is the equipment, not the personnel.  These pontoon photos are like some “walk around” we would use today to demonstrate the particulars of a piece of equipment.

Maybe the photographer was just hanging out with the engineers taking in shots of the equipment.  But this is not some point-and-shoot camera we are talking about.   These were expensive (relatively speaking) glass plate photos.  So why waste a plate on some static equipment displays?  On the other hand, perhaps these and similar photos taken at the 50th New York Engineer camp were intended to help Benham illustrate his reports.

Something I’ve learned over the years – when studying Civil War photographs, it is just as important to know the “why” story as the “what” of the subject.

Fortification Friday: Permanent or Field Fortifications?

Some time back, a reader suggested that I post about the various terms used to describe fortifications.  Sounded like a good idea, so let me kick off this first “Fortification Friday.”

For starters what is a fortification in the context of the Civil War.  Well the dean of fortifications, as far as the American experience goes – Dennis Hart Mahan wrote in his 1856 Treatise on Field Fortifications:

All dispositions made to enable an armed force to resists, with advantage, the attack of one superior to it in numbers, below to the Art of Fortification.

This means used to strengthen a position, may either those presented by nature, as precipices, woods, rivers &c., or those formed by art, as shelters of earth, stone, wood, &c.

Interesting here that Mahan pins the use of fortifications to the side with inferior numbers.  Fortifications were combat multipliers, enabling a handful of men to represent a strength beyond their raw numbers.  But does this mean Fortress Roscrans (the largest enclosed fort built during the war) or the Defenses of Washington during much of the war, where the garrison technically outnumbered any potential adversary, were simply “outposts”?  Perhaps at the strategic measure, but those fortifications were designed to allow a small force posted at points around the perimeter to hold off a deliberate, focused attack by a larger enemy force.  Or a better way to put it – a guard force on the perimeter could hold the enemy advance until the full force of the garrison arrived.

In his writings, Mahan further broke down the art of fortification into two disciplines – permanent fortifications and temporary (field) fortifications:

If the artificial obstacles are of a durable character, and the position is to be permanently occupied, the works receive the name of Permanent Fortification; but when the position is to be occupied only for a short period, or during the operations of a campaign, perishable materials, as earth and wood, are mostly used, and the works are denominated Temporary or Field Fortifications.

Clearly Fort Sumter and Fort Moultrie were permanent fortifications.  But Batteries Wagner, Gregg and those on Sullivan’s Island?  I’d argue those are in one sense permanent, since the intent was those works would defend Charleston for an indefinite period of time, despite the use of temporary materials.  In a revised version of Mahan’s original text on Permanent Fortifications, James Mercur introduced the permanent fortification:

The term permanent fortification is applied to those defenses which, constructed of materials of a durable nature, and designed for permanent occupancy by troops, receive such a degree of strength that an enemy will be forced to the operations either of a siege or a blockade to gain possession of them….

The object of such defenses is to secure the permanent military possession of those points, either on the frontiers or in the interior of a state, which must, at all times, have a well-defined bearing on the operations of a defensive or offensive war.

In that regard, Battery Wagner, Battery Gregg, and the additional batteries built on Sullivan’s Island were part of a system of permanent fortifications around Charleston defined to hold a coastal frontier.

Delineating the properties required of permanent fortifications, Mahan continued to list the conditions a defender must attain to properly setup these permanent defenses:

  1. Strength to resist open assault by ordinary means.
  2. Sustainable shelters to protect troops, armament, provisions, and magazines.
  3. Laid out so that all exterior points within range can be swept by cannon fire.
  4. Secure means of communication and movement of troops within the defenses.
  5. Configured to allow the defender to dispute any attempt to occupy, “every point both within and exterior to the defenses.”

In those measures, Battery Wagner was a failed, but flawed, permanent fortification.

But let’s go back to the force multiplier factor granted by fortifications.  Mahan considered the base element of the fortification, be that permanent or temporary, to be the intrenchment (I’ll stick to his spelling if for nothing else to annoy those pesky grammar-istas out there).  As he wrote in the 1856 Treatise:

The general appellation of Intrenchments is applied to all field works; and a position strengthened by them, is said to be Intrenched.

To enable troops to fight with advantage, the intrenchments should shelter them from the enemy’s fire; be an obstacle in themselves to the enemy’s progress; and afford the assailed the means of using their weapons with effect.  To satisfy these essential conditions, the component parts of every intrenchment should consist of a covering mass, or embankment, denominated the parapet, to intercept the enemy’s missiles, to enable the assailed to use their weapons with effect, and to present an obstacle to the enemy’s progress, and of a ditch, which, from its position and proximity to the parapet, subserves the double purpose of increasing the obstacle which the enemy must surmount before reaching the assailed, and of furnishing the earth to form the parapet.

So look at fortifications as the counter to both firepower and mobility.  A good Intrenchment would stop the enemy’s movement AND deflect his fires.  A fortification was the preventative applied against the enemy’s artillery. Or conversely, artillery was the direct solution to an intrenched enemy.  Keep that in mind when reading about the soldiers rapidly building field fortifications during actions from 1863 on.

As to the proper evaluation of a fortification’s value, in what we might consider doctrine today:

Intrenchments should be regarded only as accessories to the defense of a position. They are inert masses, which, consuming a portion of the enemy’s efforts, and detaining him in an exposed situation to the fire of the assailed, insure his defeat.

Let’s put emphasis on that last bit.  Mahan did not propose to his students (and you know who those were) that they stand their troops behind works to simply throw the enemy back.   No, he suggested an active defense.  The intrenchments were “accessories” that enabled the strong counter-punch.

Shades of some 20th century doctrine, perhaps?

(Citations from Dennis Hart Mahan, A Treatise on Field Fortification, New York: John Wiley, 1856, pages 1-2; and Mahan’s Permanent Fortifications, edited by James Mercur, New York: John Wiley & Sons, 1888, pages 1-2.)