GEOLOGIC CONTROL OF THE ARMIES
Fortifications at Fort Hill and at South Fort, as well as at intermediate places along the Mississippi bluff within the city limits, were so well nigh impregnable that a direct attack was not considered practicable by the Federals. By descending the Mississippi to the mouth of the Yazoo at that time, and by ascending this tributary to a point nearest the bluff (Haynes Bluff), the Federals hoped to penetrate the swamps and bayous and to reach dry land, but were severely repulsed. Later the Federals attempted to cut a canal and thus form a cut-off, leaving Vicksburg on a large meander curve, much as the river has subsequently done of its own accord. Failing in this attempt, the Federals marched their forces from Millikin Bend to the vicinity of Grand Gulf, allowing their boats to attempt the feat of drifting by the Confederate batteries under cover of darkness. Most of the boats succeeded in running the forts, and later picked up the Federal army, landing it at Bruinsburg. From this position the Federal forces marched north to attack Jackson and then Vicksburg from the rear.
And now comes into action the geologic forces which played such an important part in the investment.
Near and at the northern edge of the city, as the maps show, are two streams, Glass Bayou and Mint Spring Bayou, which flow in a westerly direction more or less parallel with each other. For their length and for the volume of their waters, both have cut enormous valleys of great depth and steep walls.
Along the ridge constituting the southern or left valley wall of the more northern of these two valleys, Mint Spring, the Confederates took up their position and entrenched in the Loess, the most ideal of mantle rock for rapidity in excavation and for stability of vertical walls. From the head of Mint Spring valley, they extended their line southward along the ridge constituting the west or right wall of one of the tributary valleys of Glass Bayou. From Fort Hill on the Mississippi bluff, their line extended east and thence south unbroken topographically to the crossing of the main valley of Glass Bayou near the old Jackson Road. On the side of the valley opposite these various positions of the Confederates, the Federals took up their position and likewise entrenched in the Loess. Between these parallel lines was no level way of approach other than the narrow transverse ridge forming the divide between the headwaters of Mint Spring Bayou and Glass Bayou. This transverse ridge is a part of the Graveyard Road and was actually used as the Ewing approach.
Just south of the point of crossing of Glass Bayou valley by the Confederate line is the old Jackson Road (Figure 3) extending along a ridge, which connects the two lines of trenches. Along this road is a second place, where either side could assault the other along a some what level ridge.
From Jackson Road the valley of Stouts Bayou drains south by southwestward almost to the Mississippi at the southern edge of the city. The left or east wall of this valley forms a ridge extending unbroken likewise almost to the very bluff of the Mississippi. Along this ridge the Confederates entrenched, thus encircling the city from bluff almost to bluff with a topographically unbroken trench, save for the crossing of Glass Bayou at Jackson Road.
For nearly half of the distance from the Jackson Road ridge southwestward toward the Mississippi bluff, a number of successively lower and lower tributaries of Big Bayou (Durden Creek) head upward toward the ridge, bearing the Confederate trenches, in such a manner as to form along their headwater stretches a succession of headwater valleys, the whole being a linear composite valley parallel with the ridge on which the Confederates were entrenched. On the side of this valley opposite the Confederates, the Federal forces took up their position and entrenched in a parallel line of trenches. Between the two opposing trenches was only one ridge approach; namely, the Baldwin Ferry Road through the Hebrew Cemetery near the Alabama and Vicksburg Railroad.
For approximately two-thirds of the length of the line of defense trenches, therefore, the Federal line was on the side of a deep valley opposite to, and parallel with, the Confederate line. Throughout this entire distance only three transverse ridges, the Graveyard Road ridge, the Jackson Road ridge, and the Baldwin Ferry Road ridge, connected the two opposing lines of trenches. Consequently, it was necessary that the Confederate trenches be heavily fortified at these three places, for at most other places, even though the steepness of the slope did offer protection at some, it was necessary for either attacking army to descend a steep valley wall and ascend the opposite steep valley wall in the face of a brave entrenched foe. Needless to say, the Federals' attempt to capture these special fortifications led to the hardest and bloodiest fighting along and near these three ridge approaches.
For the remaining third of the encircling line, the outward flowing tributaries head upward toward the ridge of the Confederate trenches at right angles to it, thus forming short spur ridges between them. Save for a short distance south of Kentucky Avenue, the Federal trenches were, consequently, not dug in a parallel position. Rather they were dug as a series of zig-zag trenches along the crest of some of these spur ridges and as a series of short crescent-shaped trenches across others.
Needless to say, these separate positions of the Federals in their separate trenches and along their separate ridges of approach called for an entirely different strategy of warfare than did the continuous parallel trench position. Obviously, therefore, for all these reasons, the angularity of the valleys in the loess-covered region absolutely controlled the disposition of these two great armies.
Notwithstanding the fact that before the actual siege began, the Confederates had withdrawn to a shorter arc about the city, the other fact remains that both the outer and inner positions were determined by the topography of the region. And the nature of the topography, in turn, was determined largely by the type of the material out of which it was carved. And the type of the material, in turn, was determined in this instance, largely by the work of the ancient glacier. Accordingly, as stated in the beginning, the positions of the great armies of Pemberton and Grant were determined untold ages ago primarily by the work of this ancient glacier.
Last Updated: 18-Jan-2007