Comparing the two Pembertons: A study in river defense

While discussing Beauregard’s board of general officers considering the defenses of Charleston in March 1863, one portion of the report which I highlighted was in regards to Fort Pemberton.

The board are unanimously of opinion that the present location of Fort Pemberton is a mistake, and that it gives an enemy, if he chooses, an opportunity of landing and commencing his regular approaches toward the interior defenses of James Island at his leisure and with comparative security.

That particular fortification was named for General John Pemberton. Of course by March 1863, Pemberton was not around Charleston to respond about the improper placement of the fort that carried his name. However, around this same time 150 years ago another Fort Pemberton, about 550 miles or so west of Charleston, factored into the news from the front. And that fort was well placed.

Out in Mississippi, the “western” Fort Pemberton defended a section of backwater where a bend of the Tallahatchie River neared the Yazoo River. The neck of slightly higher ground between the rivers offered position to post a defense against a Federal force aimed at gaining the rear of Vicksburg. But before I bit off more than I can chew in one post, Civil War Gazette has a very detailed series covering the Yazoo Pass Expedition.

What interests me today is the difference in the evaluation of these two forts – one arguably poorly sited for the defensive needs of Charleston, and the other putting the Federals in a difficult spot.

First let’s look at Fort Pemberton on the Stono River:


The general trace of the fort is outlined in red. As this is a Federal map, I’m not convinced that was the exact outline, but it will do for this examination. The South Carolina fort included bastions mounting heavy guns. The arc of fire allowed for guns in the left most bastion is shown above in green. To put this in plain English, one bastion had to cover the most likely approach of Federal gunboats. The main problem with the location of Fort Pemberton is it offered no overlapping fields of fire.

Now consider the “Yankee” map showing Fort Pemberton on the Tallahatchie:


Again, the fort is in red. And again, I’d take the exact plan of the fort with a grain of salt. But since the fellows who drew this map had come under the guns of the fort, I’d put some weight to the arrangement of the guns. In this case, I’ve drawn green arrows to depict the direct fire from three tiers of batteries upon the river channel. Notice the rather nice convergence and how well those guns cover far up the “reach” above the bend. Civil War Album has some excellent site photos of Fort Pemberton (Mississippi), to include a panorama looking from the fort towards the “neck.”

The nod goes to the defenders of the Tallahatchie. But before we start making a lot of conclusions, keep in mind the surrounding terrain. Outside Charleston, the marshes offered wide fields of view from even a slight elevation. Few trees of any size blocked fields of fire along the Stono. But in the Mississippi River Delta, heavy timber constrained the view. Along the Tallahatchie, the river offered narrow fields of fire. In both cases, the target was gunboats operating within a river channel. The most important consideration, therefore, was to place the maximum possible firepower on the most likely approach channel.

Regardless if the location was Mississippi River bottomlands or the brackish tidal rivers on the coast, well placed fortifications could turn an ordinary river bend into a Gibraltar. On the other hand, poorly placed fortifications became overhead to a defender stretched thin.