Vicksburg is one of the Confederate cities that obsessed Union war planners. From the fall of Memphis in June 1862 until its capture in July 1863 Vicksburg remained the Northern most Fortress on the Mississippi river. Along with its twin fortress in Louisiana at Port Hudson it managed to keep enough of the Mississippi river Confederate to enable commerce and supply between the eastern and western Confederacy. With its fall, the south would be split in two, trade with Mexico would stop, reinforcements from Texas, Arkansas, Missouri and most of Louisiana would stop, the union would gain access to Red River (a major navigable avenue of advance for the union) and the Midwestern states still in the union would regain their primary route of trade. Vicksburg mattered.
Of these two forts, Vicksburg was by far the more likely to be attacked. This is in part because of the flow of the Mississippi itself. Rivers move with considerable speed. One could travel from for Illinois to the Gulf of Mexico in a matter of weeks strapped to a log. At Vicksburg the river moves at about 3 mph. Heavily laden steam transports of this era wouldn’t have moved much faster than 10 Miles per hour. Given this, a ship passing Vicksburg would spend half as much time under the Vicksburg guns as they would the guns a Port Hudson. Furthermore, a ship disabled by Confederate fire, would continue to float downstream passed that fort. In contrast, a ship disabled passing Port Hudson would then float BACK down stream, giving all the fort’s guns a second round. And this while moving at the same speed as that log we strapped you to back in Illinois. Why attack upstream when you can attack down?
An attack on Vicksburg is made all the more attractive given its location. Port Hudson lay upstream on New Orleans and required sea transport for both troops and supplies. The nearest rail supplied Union port lay lay in Maryland at Baltimore ,an immense distance to shuttle troops and supplies. In contrast half of the northern states are connected to Vicksburg via the Mississippi River. The transport of troops and supplies to that point made it the most easily accessed battlefield of the war, or would have had it not been for the quirky topography in that part of Mississippi and the 30,000 Confederates stationed there to keep it out or Union hands.
The Mississippi Delta
Just above the city of Vicksburg, the Yazoo river meets the Mississippi. The Yazoo flows roughly parallel to the Mississippi for nearly two hundred miles (until just below Memphis in Tennessee.) Between the two rivers lies one of the great American swamps; The Mississippi Delta.
Too wet to march through and too dry to navigate by boat, it could only be avoided. And at 175 miles tall by 65 miles wide it made a considerable thing to go around. Traveling around the delta had is perils as well though. In November of 1862, Grant marched an army through Mississippi from Memphis around the east side of the Delta only to discover that 200 miles is too far to supply troops overland. In just a week of travel Grant’s ponderous supply line was raided by both Nathan Bedford Forest and by Earl Van Dorn leaving Grant no choice to go back the way he came on short rations. An attack on Vicksburg would have to me made from the river itself.
The Yazoo River and Haines Bluffs
So… given that troops could not be marched overland from Memphis, the next logical approach would be landing them from the river itself. South of the Yazoo, the land on the east bank of the Mississippi is all swamp until finally it reaches the bluff that Vicksburg itself is built on. The Yazoo though is sufficiently navigable and far enough north of Vicksburg to be be safe from its guns. An amphibious landing at any point along the east bank of that river would put troops within reach of Vicksburg. An attack up the Yazoo was a seriously dicey proposition as General Sherman and his Corp discovered in December of 1862.
First, attacking up the Yazoo can be done but at that awesome upstream disadvantage enjoyed by Port Hudson. An attack launched up the Yazoo would be done in plain sight of Vicksburg and at a blistering 6 or 7 miles an hour. To make matters worse, the river is not straight but the road connecting all landings south of the river is. It simply is not possible to surprise anyone with a naval landing along the Yazoo.
To make matters worse, the east bank of the Yazoo is a long, uninterrupted bluff upon which an assault must be staged within yards of the transports dropping soldiers off. Think Saving Private Ryan with banjos. The bluffs extend so far north along the Yazoo that you may have well marched overland from Memphis by the time you reached flat/dry ground. Clearly troops must be landed south of the Vicksburg.
Passing the guns at Vicksburg
To make a landing south of Vicksburg would require troops and supplies be transported via boat past the guns at the fort city itself. This is as bad an idea as it sounds. Vicksburg sits at a commanding height above the river. Not only are its guns too high to be shot at by the ships passing beneath them but shots from these guns are of the nasty “plunging” variety.
Plunging fire sucks. Ships are built under the firm belief that only other ships will fire at them. 99.9% of the time, this is a good bet. Cannonballs shot in flat trajectory at an unarmored ship will typically pass through the ship only harming what is hit by the ball itself or the splinters created by striking a wooden ship’s sides. Ships don’t like this but they can put up with a certain amount of it. Ships are only seriously sunk by shots that land below their waterline. This is tough place to put a cannonball given how much water decelerates shells. Plunging fire would not be aimed at the side of a ship however, It would be aimed at the deck. Cannonballs would, again, pass straight through the ship and exit the opposite side. This time however, the opposite side of the ship is the bottom of the ship. Bad.
Ironclads faired little better. Armored against fire from enemy ships, Ironclads rarely had enough deck armor to hangout overlong under the high sited guns of a river fortress. Those that did have good deck armor tended to have sloped armor that would reflect shot and shell up and over the ship. This slopped armor (see picture below) was purposely angled under the assumption the fire was coming in flat. Plunging fire would hit sloped armor straight on and do more damage than level fire.
I should also point out that fortress guns tended to be big…
Oh… and the river in front of Vicksburg hairpins…. If ya don’t get sunk the first time… no worries… try again!
South of Vicksburg
So, having passed Vicksburg…. somehow… the Union commander would be faced with a similar problem that he faced on the Yazoo. The land south of Vicksburg was either swampy and unsuitable for landing or bluff covered and well guarded (or both). Any landing near to the fortifications would bring out a ton of Confederates to prepared positions along the east bank of the Mississippi. The outer defenses of Vicksburg extended quite effectively for over dozens of miles down river.
Once you get past the defenses of Vicksburg a number of rivers empty into the Mississippi (the Big Black and Bayou Pierre.) These rivers, while too small to navigate, are too big to cross. The land around them is also quite swampy and altogether unsuitable for armies. You could land south of them but to get to the bridges across these rivers you have to go inland 50 or 60 miles. Trekking this far inland creates a variation on same problem that made the march from Memphis such a challenge! Supply marched this far inland would be perilously vulnerable to raids and partisan attacks.
So… Vicksburg can quite literally only be approached by an army from the east. The Delta, swamps, bluffs, forts, and 30,000 Confederates all conspired to make the Fortress of Vicksburg the mother of all tough nuts.
In the summer of 1863 U. S. Grant solved the problem of Vicksburg. And he did it without inventing paratroopers… Stay tuned!