Fortification Friday: Blockhouses as Safety Redoubts in the Fort

When I say “blockhouse” many of you might be thinking about favorite childhood playsets:


Certainly suitable for the defense of the bedroom in the face of the elite Confederate Plastic Brigade, or perhaps the indigenous Plastikawi tribe.  But… something that could not hold against the Green Army Men armed with bazookas and flamethrowers.

Kidding aside, the playset fort is pattered after real structures from American history.  The blockhouse was not unique to America, as it was a form brought over by Europeans.  However, the blockhouse became the preferred fortification on the North American continent from colonial times right up to the 20th century.  Blockhouses work well in situations where the enemy is unlikely to possess anything larger than light artillery.  The interior of the blockhouse was easily adapted into living quarters.  Conversely, living quarters (houses) might be easily adapted into a blockhouse.  Those, and other qualities, made that form of fortification popular on the frontier.

The popular image of a blockhouse is something made of wood.  But stone, or even adobe, might be used instead.  Since wood was in abundance on the early American frontier, we tend to see a lot of structures like this one:

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This is recreation of Fort King George, Darien, Georgia (a place with many, many layers of history).  In this particular case, the blockhouse served several roles – a high observation platform over the marsh, a platform for covering fire to protect approaches to the fort, and, in the event the works were overwhelmed, a final defense for the fort’s garrison.

It is that last function that Mahan had in mind when considering interior arrangements for field fortifications.  Blockhouses were a structure that could be used for what he called “safety redoubts”:

Safety Redoubt.  In enclosed works a place of retreat, into which the troops may retire in safety after a vigorous defense of the main work, will remove the fears of the garrison for the consequences of a successful attack of the enemy, and will inspire them with confidence to hold out to the last moment.

This interior work, which may be very properly be termed the keep, can only be applied to works of large interior capacity.  It may be formed of earth, or consist simply of a space enclosed by a defensive stoccade, or palisading.  In either case it should be about four feet higher than the main work, to prevent the enemy from obtaining a plunging fire in it from the parapet of the main work.

Let us pause here before going to Mahan’s formal introduction of the blockhouse.  This “hold out to the last” is a notion steeped in 19th century presumptions about how a siege would play out.  A garrison “holding out” would force the enemy to make a direct attack on the parapet… in other words, to get up close, personal, and… well… very violent with the defender.  And in that violent melee, the defender was not exactly in a position to call a “time out”.

The safety redoubt, or keep, was a place to retreat and, more importantly, force a pause in the action.  And from the keep, within that pause, the defender might negotiate a cessation of the fight, with honor.  Thus we see how that might allay fears of “consequences” for the garrison.

That in mind, Mahan offered his preference for the keep:

The best arrangement for the keep is the construction termed the block-house. This work is made of heavy timber, either squared on two sides or four; the pieces which form the sides of the block-house are either laid horizontally, and halved together at the ends, like an ordinary log-house, or else they are placed vertically, side by side, and connected at the top by a cap-sill. The sides are arranged with loop-hole defenses; and the top is formed by laying heavy logs, side by side, of the same thickness as those used for the sides, and covering them with earth to the depth of three feet.

Mahan offered this figure as an example of a blockhouse:


This perspective is looking at the blockhouse along with a cross section of adjacent works and structures.  Rather busy.  This section is along the line a-b from Figure 44:


The combined caption reads:

Figs. 43,44. Shows the plan and section of a block-house of upright timber.  The plan is made to exhibit a portion of the top complete; the timber covering the top; the arrangement of the cap pieces; a plan of the loop-holes; and a plan of the camp-bed. Fig. 43 exhibits, in a like manner, a cross section of the block-house and ditch; with interior and exterior elevation.

We will go into the particulars for construction in later posts.  What is important to identify here is the functional nature of this blockhouse.  Just as with the colonial-era Fort King George, we see a blockhouse adjacent to a ditch and other defensive structures.  One might say the blockhouse filled up the fort’s interior.

For an attacker, this presents a serious tactical problem.  One might defeat the defender on the parapet.  But the parapet would be a dangerous place to make a living with the blockhouse overlooking all. So you see where a “pause” would be in order.

Keep in mind, within this discussion of keeps, Mahan was not stating or suggesting that blockhouses only be constructed within and in conjunction with elaborate field works.  Rather that he offered that a blockhouse was a structure that served well as a keep inside a larger set of works.  We see that usage applied by his students during the Civil War.  Looking back again to Fortress Rosecrans:


We see Redoubts Schofield, Brannan, T.J. Wood, and Johnson within the interior.  One wartime report described the arrangement as, “… strong against attack, being defended by large keeps, which deliver their fire upon every part of the interior.”  I would further add that most of the lunettes on the perimeter of this vast fortress included blockhouses.  So there were multiple “keeps” within a depth of the defense.  Keep in mind the scale of this fortress.  The safety redoubts, named above, were armed with 30-pdr Parrotts and 8-inch siege howitzers.  The Confederates would need to bring a large amount of iron in order to suppress the fort’s garrison.

But the size of this work was perhaps its weak point.  After the Army of the Cumberland moved further south, through the summer of 1863, there the need to keep this fortification in order was taxing, in terms of manpower. An 1865 report suggested all be reduced to simple blockhouses covering the bridge and depots.

That circles back to the point about blockhouse usage.  As said before, Mahan was not suggesting the only place to use a blockhouse was as a fort’s keep. But as his text was focused on field fortifications, the focus was on that function.  We will see blockhouses enter the conversation in regard to detached defenses in particular.  Furthermore, the post-war instructions would place more emphasis on the detached, singular blockhouse.

(Citations from Dennis Hart Mahan, A Treatise on Field Fortifications, New York: John Wiley, 1852, pages 62-3; OR, Series I, Volume XLIX, Part 2, Serial 104, page 502.)


Fortification Friday: “a redan or a lunette, is thrown up on the exterior to cover the outlet”

Before we close the discussion of openings for forts (see what I did there?), let me circle back to compare Mahan and Wheeler in regard to one of the fine points considered.  That being the use of a detached redan or lunette in advance of the outlet.  Recall that in pre-war writing, Mahan suggested:

In very frequented passages, a redan or a lunette, is thrown up on the exterior to cover the outlet, and thus ensure its safety in case of surprise.

And Wheeler, in the post-war, mentioned a similar arrangement, but perhaps narrowed the application to those larger outlets, for sorties, where simple interior traverses would not be practical.

Mahan offered two figures that illustrated the redan to the front of an outlet:


Figure 48 offers a wide redan in front of an outlet, which is further covered and flanked by by the “horns” of the larger work.  A very well protected outlet, we might say.  Mahan considered this a Redan Line.

On Figure 49, we see much more complexity.  Particularly with the defensive lines of fire.  The outlet is nested within a redan of a larger line.  On both sides are faces within redans of differing angles. This is considered a Tenaille Line – a proper definition we will discuss later.  But the point being the covering redan, to the front of the outlet, was absolutely necessary here in order to protect that weak spot.  The covering redan is somewhat off center of the outlet, perhaps to limit exposure at the expense of accessibility.

Wheeler, as you may recall, gave us only a simple rendition of the covering redan:


The question I have in regard to these advanced, detached “parts” covering openings is… just how often were these employed during the Civil War?

When examining surviving earthworks, we often find the area around the outlets obliterated.  Sometimes, due to necessity, that is done to facilitate visitor access.  But more often, just a case where the structures around the outlets were the most susceptible to erosion.

And when examining wartime plans, we see some use of these redans… but more often not.  Consider Fortress Rosecrans outside Murfreesboro:


This was, some have said, the largest fort built during the war.  And in this plan we see examples of many features suggested by Mahan.  Specific to the outlets, we see up near the top that Battery Cruft was a detached lunette (maybe a “half lunette”) covering an outlet.  Elsewhere, such as next to Lunette McCook at the bottom right, we see an outlet (an existing road) without a covering redan or traverse.  Though we do see obstacles erected to the right of Lunette McCook.  And certainly that named work was positioned to dominate the approaches to the outlet.  Furthermore, what you don’t see in my “snip” are works in advance of the fortress that covered the railroad and road.  Though those were oriented south and not regarded as covering the outlet in question.

Another plan to consider is from Virginia, at Deep Bottom:


Here we see five road crossings at the main line of the works.  One of those is blocked entirely by a redan.  The other four (including one that appears to be a path cut just to clear a redan) have no traverses or covering works.  Just obstacles placed in front.

If we are assessing the protection of outlets, with Mahan’s suggestions in mind, we find a mixed application of those covering redans.  Seems to me the use of that sort of feature was based on the engineering assessment of need.

Now considering such use under Wheeler’s suggested implementation, let’s look to the location of a few large scale sorties.  First, how about the works were the Crater assault was mounted:


And further around the lines, and further forward in the historical timeline, to the sector around Fort Mahone:


And to the left of that sector near where the Federal Sixth Corps mounted their sortie:


Now the scale of these maps mean these are not so much “plans” as operational maps.  So we know there are structures that escaped the pen here.  But what stands out, with double underlines, is the use of something far more elaborate than Mahan and Wheeler discussed.  We see entire sections of works advanced in a manner to provide staging grounds for those formations preparing for the assaults. Major assaults, mind you, involving whole divisions.  These were, you see, works built for the offensive.  Grand offensives!  In that light, might we say the entire Federal line was one large “covering work” in front of an array of staging areas and supply depots?

The Guns at Stones River

Happy New Year to all!

Let me kick off 2013 in good order with what has become my practice on sesquicentennials – a virtual tour of Stones River battlefield by way of the artillery.

Included in this set are original guns at field displays, replica guns, memorials in the cemetery, and museum displays.  You’ll want to click on “view larger map” to see the full set.  One replica gun at Fortress Rosecrans is outside the map seen above.

This map depicts the locations of artillery displays as of “now”.  After spending the last few days on the battlefield enjoying sesquicentennial events, I can proudly say “that is where the guns are located.”  Well as of now at least.  I have noticed several changes to the arrangement since my last visit in 2010.  In fact, the whole park has changed, with a new entrance at the south end and an improved tour route.  Several sections of the old tour road are now walking trails.  All good for those of us who like to get out and experience the field instead of just speeding through.

One notable change to the cannon placement.   One of the more popular displays was the Wiards on broken carriages at the Slaughter Pen.

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A pair of rare guns in a rather unique display.

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I noticed, with some misgivings, these guns are not in place among the rocks.  At least not during the sesquicentennial events.  Instead, two Wiards stood at displays around the Slaughter Pen, but not actually among the rocks.

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True cannon aficionados will note the form of the carriage.  Yes, proper replica carriage as designed by the inventor of the gun – Norman Wiard.  There are several interesting features of the carriage, which is the fodder for future blog post.

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I suspect, but was not able to confirm, that the two guns on display currently are different from the “broken carriage” set.  The park has two each of the 2.9-inch and 3.67-inch calibers, or at least did at one time in the past.  Perhaps we’ll see the broken carriage set returned at some future date.  Although pointed in the wrong direction, the arrangement brought many a visitor to a pause for contemplation.

So please take a moment on this first day of the year to think back 150 years.  January 1, 1863 was a day marked by many important events.  The battle of Stones River was one of them.  If you can’t visit the battlefield, then I’d invite you to take a virtual stroll by way of the cannons.

Stones River: The Preservation Story

Yesterday morning, we made a few stops prior to reaching Stones River National Battlefield, proper, and the sesquicentennial events.  One of those was a rather typical highway intersection.

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Gersham Lane and Franklin Road

On December 29, 1862, Federal cavalry pressed Confederate skirmishers away from this intersection.  The following day troops from Brigadier General Richard Johnston’s division of Major General Alexander McCook setup positions here.  The position was, for all practical purposes, the right flank of the Army of the Cumberland when the Confederate assault stepped forward on the morning of December 31.  This was the first objective in General Braxton Bragg’s attack plan.

But today this is about two miles, direct line, from the southern boundary of the Stones River National Battlefield.  In between is a school, shopping malls, residences, and a major interstate highway.  All ground contested during the battle.  Indeed many important sections of the battlefield were not included within the park boundaries. That begs the question – why wasn’t this major battlefield better preserved?

Let me offer the short version of that story here, but recommend Stones River National Battlefield Historic Resource Study by Sean Styles for further reading.  The story of the battlefield park starts in during the war.  Like many battlefields, a National Cemetery established during the war was a presence, giving the government at least some interest in the locality.  But a wartime memorial also served to attract visitors and veterans to the battlefield.

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Hazen Monument – the oldest surviving CW battlefield monument

The Hazen Monument, built during the war by veterans of Colonel William B. Hazen’s Brigade at the Round Forrest, where they fought with distinction during the battle.  The proximity of this monument and the national cemetery, just to the northwest, and the railroad line naturally made the site an attraction for travelers along that line.  That also eased logistics for veterans’ reunions.

Working along those lines, in 1906 the Nashville, Chattanooga, & St. Louis Railroad established a memorial on the other side of the railroad.

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Artillery Monument

The railroad also set aside the remains of Redoubt Brannan, visible from a passing train, as an attraction.

During the 1890s, in what historian Timothy Smith calls the “Golden Age of Battlefield Preservation”, Stones River was among the plans for additional reservations beyond the original five (Gettysburg, Shiloh, Chickmauga-Chattanooga, Antietam, and Vicksburg).  The Stones River Battlefield and Park Association secured options on several thousands of acres of land.  Prospects looked good, given the lobbying power of the veterans.  But despite several bills drafted, the proposal never gained traction.  Proponents were checkmated in 1912 with a report from Charles Grosvenor, then Chickamauga-Chattanooga National Military Park commissioner, stating landmarks on the Stones River battlefield were “entirely obliterated.”  Whether that assessment was valid or not, I cannot say.  But given the extant landscape today, I’d say Grosvenor probably overlooked some features.

Not until after World War I did Congress again take up battlefield preservation.  Under the 1927 Act for Study and Investigation of Battlefields was Stones River considered again.  In March of that year, a small section of the battlefield, 300 or so acres, became part of the National Park system.  Small sections of additional acreage, transferred in the 1930s, brought the total to just under 400 acres.  Over the following decades the park benefited from several waves of improvement projects, from the New Deal’s WPA to Project 66.  But no major land acquisitions added to the land preserved within the park.

With the growth of Murfreesboro in the middle of the 20th century, development pressed on the battlefield.  The construction of Interstate 24 bisected the fields over which the action took place on December 31, 1862 (not unlike Monocacy battlefield and I-270 in that respect).  Over time, the land was, as Grosvenor said earlier, “entirely obliterated.”  But in 1992, the park nearly doubled in size with the donation of the last remaining sections of Fortress Rosecrans, opening the total park acreage to 570.  While significant of course, the fortress was a post-battle structure.

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Remains of Fortress Rosecrans

The statistic often cited in regards to preservation of Stones River is one fifth.  That is the fraction of the battlefield which lies within the national park.  As for the remainder, it is indeed “entirely obliterated.”  There is a lot of “what could have been” attached to the preservation of Stones River.  But there’s also much we should be thankful for.  One can still look across the fields and consider the actions of December 31, 1862 through January 2, 1863.