Understanding Civil War Field Fortifications

on March 28, 2014 in American Civil War, Strategy and Tactics

A fanciful depiction of the assault on Kennesaw Mountain

Hand in hand with the rifled musket, I think one of the most misunderstood tactical features of the Civil War is field fortification. The conventional wisdom is that if you put infantry behind a stone wall or an earthen embankment, they could hold off all comers so long as their ammunition held out or they were flanked. There is a nugget of truth to that, but like so many bits of conventional wisdom, the full reality is much more complicated.

The Three Features Of Field Fortification
As a rule, any complete system of fortification includes three things: protection for the defender; cleared fields of fire; and obstacles to slow or confine enemy movements. Where the conventional wisdom always goes wrong is that it focuses on the first part, takes the second part for granted, and ignores the vital, third part.

A finished system of “abatized” Civil War earthworks might look as follows. The troops would build up a dirt embankment by digging out ditches both behind and in front of said embankment. If time and timber permitted, that dirt embankment would be reinforced with logs and topped with head logs. The result was a wood-reinforced dirt wall maybe three or four feet high, but it would be higher for the defending troops standing in the ditch behind it. Head logs lining the top offered additional protection for the troops as they fired on attackers.

The ditch in front of the embankment would be the final obstacle, designed to make it harder for assaulting troops to scramble over the top. That ditch may or may not have had sharpened stakes. To create further obstacles and clear the field of fire, trees would be felled in front of the embankment with the tops facing out. If time permitted the branches of those trees would be whittled down into stakes, clearing off foliage at the same time. These became improvised abatis.

Like barbed wire in World War One, abatis weren’t intended to stop an attack. Instead, they slowed the enemy advance, keeping them under fire longer. Sometimes they also funneled the attack into “kill zones,” where more fire could be concentrated.

Overlooking Obstacles
I think the role of obstacles is so often overlooked because of the two classic examples of stone wall defense, Fredericksburg and Gettysburg. In both cases, the attackers had to cross well over a thousand yards of open ground to reach the enemy. With such a long approach, there was little need for obstacles to keep the attackers under fire longer. At Fredericksburg, the Confederates had the additional advantage of being outside the range of Federal artillery.

Yet there was an obstacle facing Pickett’s Charge at Gettysburg: the fence along the Emmitsburg Road. Although it was an organic feature of the battlefield, it had the same effect as laying abatis: delay, disorganize, and funnel the enemy. The importance of this key feature has only really come into focus in some historical studies in the last two decades.

Conversely, how partial the value of just a protective wall is can be seen in the many Civil War examples of combat in wooded terrain. Many times a defender would build up a barricade of stones and logs, but they were only somewhat better protected than the attacker, who had plenty of ready cover. Furthermore, a clear field of fire and no obstacles meant an attacker could come very close without suffering much damage. Most examples of this kind of combat saw the combatants cling on to each other at close range, blazing away with musketry and suffering slow but heavy, cumulative casualties until someone ran out of ammunition or men or darkness fell.

Fortification In Fiction
One of the underlying messages in the way I wrote the Battle of Lawrenceburg has to do with this tactical lesson. Union troops turned Coon Creek into a proper field fortress: a log barricade set behind a ravine filled with improvised abatis, with a clear field of fire of up to a few hundred yards. The Confederate attack there predictably failed.

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