Fortification Friday: The simple, effective Abattis

Abattis?  Abatis?  Abbattis?

And how do you pronounce it?  Ah-ba-tee?  Ah-bae-tus?  Or, for those in the deep south… Awe-bat-us.

How about Russian? Zaseka.  And the Russians knew a thing or two about abattis.  Their Zasechnaya Cherta was a thousand kilometer line against the Tatars, dating to the 12th and 13th centuries, built initially from felled trees.  Thus, on a grand scale rivaling the Great Wall of China, the Russians used a basic obstacle to form a defense against cavalry raids.  We find reference to felled tree or well placed limb obstacles from ancient times right up through the twentieth century.

For this post, I will stick with Mahan’s spelling of the word … Abattis, which he described as such:

Abattis. The large limbs of trees are selected for an abattis.  The smaller branches are chopped off, and the ends, pointed and interlaced with some care, are presented towards the enemy.  The large end of the limb is secured to the ground by a crochet-picket, and may be partly imbedded to prevent its being readily torn up.

One of the best methods for forming an abattis, and which is peculiarly adapted to strengthening the skirts of a wood occupied by light troops, is to fell the trees so that their branches will interlace, cutting the trunk in such a way that the tree will hang to the stump by a portion uncut.  The stumps may be left high enough to cover a man in the act of firing.

If we are particular, there are two variety of abattis described here.  The first is that of limbs arranged, and preferably pinned, in front of the works.  Mahan offered this illustration for that form of abattis:


On the left we see the pickets designed to retain the limbs. Mahan offered specific instructions for laying these sort of obstacles:

Abattis are placed in front of the ditch; in this position they must be covered from the enemy’s fire by a small glacis. They are sometimes placed in the ditch against the counterscarp.

Note on the right side of Figure 29 above the glacis.  And think about how this would work in the defense.  An attacker would advance up that glacis, every step bringing them into greater profile within the defender’s view.  At the height of the glacis, the attacker is faced with the need to descend into a mess of twisted branches…all while the defender has a clear shot.  And if the attacker does chose to deal with the abattis, all the work is done in plain view… and within range of… the defender.  At least that is how it was supposed to work against infantry and cavalry.  Junius Wheeler, in his post-war update to Mahan’s lesson plans, offered this illustration:


As for artillery, the main reason Mahan suggested the glacis is to make difficult any attempt to break up the abattis by shot or shell.  If well constructed, the glacis would serve to ricochet the projectile over the abattis.  And if the rest of the fort were properly constructed, the projectile would continue to sail over the parapet and all vital areas… expending at some point well to the rear of the defense.  We see that illustrated, in reference to the other components, in Figure 26:


The obstacle at the bottom of the ditch in this case is a small picket.  But we might refer to some wartime photos to see an abattis used in the ditch, laid against the counterscarp, as Mahan suggested:


We see an abattis laid against the counterscarp, which we are looking over, in the foreground.  In the background we see palisades and other obstacles… which we will discuss in due time.  Wheeler, writing post-war, offered one other alternative along this theme.  He suggested planting the abattis upright in the ditch as so:


The other variation mentioned by Mahan, felled trees still attached to the stump, was perhaps more so a field expedient.  As he said, perhaps where light troops were defending a wood line.  Beyond just forming a supplement to the main fortification, the abattis might be called to serve as the main line of defense in some situations:

This is an excellent obstacle in a wooded country, and admits of good defense, if a slight parapet is thrown up behind it.  The parapet may be made of the trunks of trees laid on each other with a shallow ditch, or trench, behind them; the earth from which is thrown against the trunks. In an open position it may be relied on as a security against surprise, particularly of cavalry.

Abattis were relatively simple, as far as obstacles go.  Very little effort needed to create them.  And the materials were usually easy to come by.  Likewise, once in place the abattis were easy to maintain. So we see a lot of them in Civil War photographs.  One of my favorite studies in that regard is Fort McAllister:


This is the view of Hazen’s Division attacking the fort on December 13, 1864.  Not hard to put yourself in those shoes.

We don’t see much in the way of a glacis protecting these abattis.  And these are very far out from the main fortification’s ditch.  Another point of view shows a section of abattis closer to the fort’s ditch:


I think we are have several factors involved with the placement of abattis at Fort McAllister.  To begin with, the Ogeechee River’s alluvial plain did not offer much in the way of relief for the defender’s advantage.  So to build a glacis, one needed to displace a lot of sand.   And that is sand, not earth.  And when dry, sand does not stand up well, bringing the need for some form of revetment.  Bottom line, a lot more work.

An operational factor at play is the nature of the defense.  Fort McAllister was built to stop Federal gunboats and ironclads from venturing upriver.  So its facings were strengthened accordingly.  The marshes and other natural obstacles would deter any flanking operation from a sea-based attacker. So the Federals flanked the works by way of a march from Atlanta.

Lastly, the distance of the abattis from the ditch is, I think, significant.  It being a tactical factor. By 1864 both armies were keenly aware of longer engagement ranges.  The defenders of Fort McAllister could push out those abattis and feel comfortable their artillery and musketry would range.  But keep in mind, when viewing the photos, the abattis appears to be “out far” in some sections but close in at other points.  All were, I would submit, placed with respect to tactical needs.

One more photo from Fort McAllister that reinforces Mahan’s discussion of abattis:


Look at this mass of twisted limbs and branches.  It is not the heavy limbs that Mahan may have preferred.  But it is an obstacle none-the-less.  Again, imagine having to step through that mess in order to get at the next layer of obstacle… all while under fire from the defender.

(Citations from Dennis Hart Mahan, A Treatise on Field Fortifications, New York: John Wiley, 1852, page 45.)

Marching Through Georgia, December 13, 1864: The Taking of Fort McAllister, Part 3

Sometime in the evening of December 13, 1864, Major-General William T. Sherman sent this message to Major-General Henry Slocum, commanding his Left Wing:

Take a good big drink, a long breath, and then yell like the devil. The fort was carried at 4:30 p.m., the assault lasting but fifteen minutes. The general signaled from this side to the fleet and got answers, and the vessels were seen coming up from the sound….

Later in his official report, Sherman differed mainly on the time of the assault, citing 5 p.m., continuing “I witnessed the assault from a rice mill on the opposite bank of the river, and can bear testimony to the handsome manner in which it was accomplished.”  And that short description is usually enough to pass for most mentioning the event.  Closer to the action, Brigadier-General William B. Hazen recorded:

The grounds to the right of the fort being marshy, cut through by deep streams, rendered the deployment of that part of the line slow and difficult, and was not completely effected till 4.45 p.m., at which time, every officer and man of the nine regiments being instructed what to do, the bugle sounded the forward, and at precisely 5 o’clock the fort was carried. The troops were deployed in one line as thin as possible, the result being that no man in the assault was struck till they came to close quarters. Here the fighting became desperate and deadly. Just outside the works a line of torpedoes had been placed, many of which were exploded by the tread of the troops, blowing many men to atoms, but the line moved on without checking, over, under, and through abatis, ditches, palisading, and parapet, fighting the garrison through the fort to their bomb-proofs, from which they still fought, and only succumbed as each man was individually overpowered.

Not to sound like I’m jumping on a modern commercial catch-phrase, but fifteen minutes is all it took.  But we see, in Hazen’s report, that inside those fifteen minutes was a storm of destruction.  Hazen mentioned the torpedoes for good reason.  Most of his 24 killed were due to those mines.  And the veterans who lived through those fifteen minutes remembered them long after the war.

In a letter to the National Tribune in 1901, John Scott, Company I, 116th Illinois wrote:

Being on the right of the line, we entered the fort on the lower side.  I was knocked down by one of the torpedoes, and a piece of the limb that was attached to the torpedo stuck in the corner of my left eye, which when I pulled it out caused the blood to flow.  I was soon covered with blood from head to foot.

Later, in 1907, Eli A. Weekley of Company B, 53rd Ohio wrote of his experiences somewhat dismissing the torpedoes, going as far to say none fired during the assault.  Well this sparked what we might call today a “flame war” with responses.  I would offer that the great service of Weekley’s letter was to bring forward some vivid accounts of what those fifteen minutes were like.  J.S. Horner, Company D, 30th Ohio responded to say:

I am certain he is mistaken in this statement … I remember very distinctly of jumping over a pile of fresh earth while on the charge.  The man just behind me jumped over it all right, but the man behind him struck the cap of the torpedo as he ran and it exploded and blew off his foot above the ankle joint leaving the bone bare of flesh for two or three inches above the joint. When I heard the report of the shell I looked back and saw the poor fellow as he fell back in the hole the torpedo made when it exploded.

L.C. Huffine, Company C, 30th Ohio provided a similar response affirming the injuries due to torpedoes, adding

When we got up close to the fort we saw the wires above ground, and the boys sang out, ‘Watch out!’ One exploded at the head of my company blowing off the leg of Comrade Hiram Rooney, Orderly Sergeant. He was only a few feet from me when the explosion came and my eyes were full of sand. When I could get the sand out of my eyes, I looked and saw the boys on top of the fort shooting down into it.

And C.C. Degman, Company F, 70th Ohio likewise added his view of the damage from the torpedoes.  But in his letter he also described the effort required to cross the ditch and break through the stakes planted there.

This was a serious obstacle, as the stakes could not be moved except in a few cases.  Some got thru the small openings, some were held up by comrades, and fell over, others were helped over by those on the other side.  Finally all were over, and then the command came from Col. [Henry] Phillips: “Forward, boys!”  They fired one volley and then, with bayonet in hand, leaped forward and in only a few minutes after the torpedo line had been passed were on top of the fort.

And I know that many readers will recognize the style and tone of the National Tribune, with which we must place a grain of salt (as we sometimes have to do with letters found in the Confederate Veteran, or as with any veteran’s magazine were accounts are offered decades after the events).  But there is the emphasis on the torpedoes.  All seemed to think them ghastly.  And of course at the time, Sherman agreed.  Upon seeing the injury done by those weapons, he insisted, for the second time in a week, that Confederate prisoners be employed in the disarming of the torpedoes.

As horrific as the obstacles were, the Federal casualties were small when compared to similar assaults on fixed positions – 24 killed and 110 wounded.  Part of the reason for this was indeed the faulty Confederate dispositions – the cannons en-barbette, gaps in the abitis, covered ground within musket range of the fort, and simply the small number of the garrison.  But we should not dismiss Federal success as a forgone conclusion.  Recall just over a week prior a similarly large Federal force was unable to break through at Honey Hill.  And many of the same men stopped at Cossawhatchie.  I submit the difference at Fort McAllister had to do with leadership.  Hazen ensured “every officer and man” knew what was needed.  He kept good communications with his superiors and with subordinates (with the possible exception of Second Brigade).  He used every bit of information and advice provided by Kilpatrick.  In fact, to the extent that Hazen’s attack might be called an “infantry” version of what Kilpatrick had suggested the night before.  In short, Hazen and his men deserved every accolade bestowed for success at Fort McAllister.

After the fort was taken, Sherman and Howard, along with some of their staff, crossed the Ogeechee and met with Hazen.  After a late dinner, the generals took to the water again in search of the fleet.  Soon they were on board the USS Dandelion. The next day Sherman would meet with Major-General John Foster and Rear-Admiral John Dahlgren (in that order, as Foster awoke him in the very early hours of the morning).  The Ogeechee attained, Sherman needed it cleared and opened for transports to supply his army.  He was at that moment focused on the prize of Savannah.

(Citations from OR, Series I, Volume 44, Serial 92, pages 10, 110, and 704; National Tribune, September 12, 1901, page 3; March 14, 1907, page 6; June 20, 1907, page 6; July 11, 1907, page 6.)

Marching Through Georgia, December 13, 1864: The taking of Fort McAllister, Part 2

In part 1, earlier today, I offered some background on Fort McAllister’s attackers and defenders.  Looking now to the “moving pieces” we turn to King’s Bridge.  At around 5 a.m. on the morning of December 13, 1864, the engineers stopped their repair work on the bridge to allow Brigadier-General William B. Hazen’s division to cross.  Within a few hours march, the division reached Joseph McAllister’s Strathy Hall plantation.

There Hazen posted guards, even though Brigadier-General H. Judson Kilpatrick’s cavalrymen had already ransacked the house.  The infantry column pressed on to the turn off towards Genesis Point (just upstream from Fort McAllister).   Nearing Hardwick, at the base of a peninsula formed by a wide “bow” of the Ogeechee River, a signal team went out to establish a station and communicate with the station at Cheves Rice Mill to the north.  Hazen’s infantry continued on the road to Fort McAllister, skirmishing with Confederate outposts.  Along the way they encountered several buried torpedoes on the roadway.

While Hazen’s men were marching, several other pieces were in motion (Some of the arrows are positioned to simplify the map):


To Hazen’s front, Kilpatrick’s cavalry withdrew from Genesis Point, where they’d pressed the fort’s pickets back.  Kilpatrick spoke with Hazen, providing details of the Confederate dispositions.  With that, Kilpatrick’s men split up into two columns.  Colonel Eli Murray’s brigade moved into Liberty County, moving by way of Midway.  Colonel Smith Atkins moved his brigade further south on Bryan’s Neck towards Kilkenny Bluff.  The cavalry’s task was to seek out Federal blockaders in St. Catherine’s Sound, as a contingency against failure at Fort McAllister.

At Cheves’ Rice Mill, Major-Generals William T. Sherman and Oliver O. Howard arrived to take up an advance observation post.  Captain James M. McClintock, at his signal station, observed Hazen’s movement and searched, without luck, for naval activity on the Ogeechee.  Captain Francis DeGress maintained sporadic fire on Fort McAllister with no effect other than gain the Confederate’s attention.

The arrival of Captain William Duncan on the 12th prompted Major-General John Foster and Rear-Admiral John Dahlgren to start actively looking to establish positive contact with Sherman.  Foster sent Lieutenant George Fisher, an experienced signal officer, to reconnoiter the rivers south of Fort Pulaski.  Unfortunately, as Dahlgren noted in his diary entry for the 13th, the navy was simply stretched too thin.  Not until the morning of the 13th was Fisher on board the tug USS Dandelion, a fine vessel but not the sort of warship Sherman looked for.  Not knowing where Sherman’s men might be, they began searching along the Vernon River, and then into the Little Ogeechee River.  Although the ship’s captain was wary of Confederate batteries, he did provide Fisher a skiff to get into some of the smaller creeks to a point opposite Fort McAllister.   Hearing the sound of muskets across the marshes, Fisher:

… Looked about and saw, about thee miles northwest of where I was lying in the marsh, a flag upon the top of an old rice mill, but there being no air stirring, I was unable to make out of what nature it was. I could then indistinctly see persons through a broken part of the roof, one of whom, taking hold of the end of the flag, drew its folds out so that I could see our own glorious Stars and Stripes.

Fisher immediately made his way back to the tug and asked the captain to proceed up the Ogeechee.  The time was around 2:00 p.m. with not much daylight left.

What had caused the musketry heard by Fisher was the arrival of Hazen’s lead elements at Fort McAllister’s outer line of defenses.  Skirmishers fanned out and started to engage the fort’s garrison with a purpose.  With the fort’s guns sitting above the parapets, instead of firing through embrasures, the Federal sharpshooters could harass the Confederate gunners and keep down their rate of fire.

Hazen needed time to deploy his division.  He wanted to first encircle the fort, using nine regiments (three from each brigade), backed up with three more regiments in reserve.  When all was in position, he’d launch a grand assault to overwhelm the defenders.  Hazen, as he did in most operations, did well to keep his subordinates informed as to the plan, setup control measures to reduce mistakes, and, above all, provide as much information as was available about the situation.

The plan called for Second Brigade, arriving first at the fort, to form a line anchored on the river to their left.  Next, First Brigade would sweep around to the far side of the fort and setup in position to assault from the south.  Third Brigade would file in to fill the gap  between.  The problem was, for Second Brigade, a creek cut across the line of march.  Thus the deployments were far too slow for Hazen’s, Howard’s, and Sherman’s likings.

While the infantry deployed, elsewhere the other parts of this “drama” were moving:


Kilpatrick’s cavalry moved to their new assignments.  In Liberty County, Murray dispatched the 5th Kentucky Cavalry to Sunbury (near the old Revolutionary War post of Fort Morris).  Likewise Atkins’ men reached Kilkenny Bluff.  Both forces searched for a way to catch the eye of the blockaders.

Fisher, by then back on the Dandelion, moved through “Hell’s Gate” into the Ogeechee.  The tug risked the big guns of Fort McAllister to a point just below a bend in the river.  There Fisher began attempts to signal the station at the rice mill he’d seen.

The time was around 4:30 p.m.  Tensions at Cheves’ Rice Mill ran high.  The sun was setting low in the west.  The planned assault of the fort was not yet ready.  And the fleet had not been seen.  In the words of more than one observer, Sherman was anxious if not outright nervous.  But this was right when all the moving pieces converged to turn the day for the Federals.  Observers at the rice mill noticed the smoke from the tug.  Soon Fisher was sending a query:

Who are you?
Fisher, Lieutenant.

McClintock, General Howard’s signal officer.

How can I get to you? What troops are at Fort McAllister?
Fisher, Lieutenant.

We are now investing Fort McAllister with Hazen’s division.
Howard, General.

General Howard:
What can we do for you? We are ready to render you any assistance.
Foster, General.  Dahlgren, Admiral.  Fisher, Lieutenant.

General Foster:
Can you assist us with your heavy guns?
Sherman, General.

General Sherman:
Being only a tug-boat, no heavy guns aboard.
Fisher, Lieutenant.

(And I’ve often wondered what Sherman’s real thoughts were, receiving that last line from a lowly lieutenant!)

The dialog cut short by Fisher’s last reply, McClintock now signaled to Hazen’s station:  “It is absolutely necessary that the fort be taken immediately. The Stars and Stripes must wave over the battery at sundown. Sherman, General.”  With that, Hazen knew he’d exceeded the time allowed for deployment.  He had to go in even if Second Brigade was not in position:


With some of the luck which had followed the men throughout the march, Second Brigade fell into position just as the bugles sounded to start the charge.

The assault was not a forgone conclusion by any means.  Nor was it simply a dash for the parapets.  The troops first had to close several hundred yards of cleared ground.  That reached, they had to wrestle through several layers of abatis and felled trees.  Exiting that obstacle, there were mines planted.  Then they had cross the ditch, breaking through the palisades in the way.  (Recall the photos from the earlier post.)

But these were hardened veterans who’d seen many assaults of this type in the past.  When the bugle sounded, they surged forward.  With that, allow me to pause and break this post up for ease of reading.  I’ll take up the assault and offer an assessment in part 3.

(Citations from OR, Series I, Volume 44, Serial 92, page 753.)