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The Engineers at Vicksburg, Part 25: Siege Engineers

U.S. Army Engineer Research and Development Center, Historian
Published July 6, 2017
Thayer’s Approach to Confederate fortifications on Fort Hill Ridge is visible from the tunnel sappers dug through a ridge on approach. The National Park Service at Vicksburg National Military Park has preserved and restored the tunnel for visitors to see first-hand the magnitude of the sappers’ task.

Thayer’s Approach to Confederate fortifications on Fort Hill Ridge is visible from the tunnel sappers dug through a ridge on approach. The National Park Service at Vicksburg National Military Park has preserved and restored the tunnel for visitors to see first-hand the magnitude of the sappers’ task.

The Confederate defenses of Vicksburg are detailed on this detail of a postwar map (including the six forts Union engineers and sappers were working to defeat),

The Confederate defenses of Vicksburg are detailed on this detail of a postwar map (including the six forts Union engineers and sappers were working to defeat),

Introduction:

Engineers in Union blue and Confederate gray played a prominent role in the Vicksburg campaigns of 1862-1863. Although their contributions have largely gone unnoticed in published works on the campaign, the stories of these men and the fatigue parties that toiled under their supervision are worthy of note and will be detailed in this series of articles.

Part 25: Siege Engineers

As siege operations began, Capt. Frederick Prime, the Army of the Tennessee’s chief engineer, had his concerns. Besides himself, Lt. Peter C. Haines, chief engineer of McClernand’s XIII Corps, was the only other officer belonging to the Corps of Engineers then serving in an engineering billet with the army. It would be impossible for these two men to superintend the thirteen approaches that were begun at different points along the investing line that extended twelve miles from flank to flank. To assist these men, officers with an engineering background, either military or civil, or associated professions such as surveyors and architects, or those with construction experience were pressed into service to direct individual projects.  

Six roads led into Vicksburg from various points of the compass and Confederate forts guarded each one. Most, but not all, of the Union approaches were directed against these forts in order to seize the roads and gain access to the city. The main Federal efforts were concentrated along the Graveyard Road, Jackson Road, and Baldwin’s Ferry Road, which were the focal points of the XV, XVII, and XIII Corps respectively. These approaches will be discussed from north to south.

Positioned on the north end of the investing line, or Union right, were the men of Maj. Gen. William T. Sherman’s XV Corps, the chief engineer of which was Capt. William Le Baron Jenney. The Fairhaven, Massachusetts, native had been a civil engineer prior to the war who had studied at the prestigious Lawrence Scientific School at Harvard. He then continued his engineering and architecture studies in Paris at the Ecole Centrale Des Arts et Manufactures.  While Jenney directed efforts against the Stockade Redan complex of fortifications guarding Graveyard Road, Capt. Herman Klostermann of the 3rd Missouri Infantry opened an approach across Mint Spring Bayou and up Abbott’s Valley toward the 26th Louisiana Redoubt.  Working under Klostermann’s direction was the pioneer company of the corps’ First Division and line troops from Brig. Gen. John M. Thayer’s Brigade. Thus, the approach was known as Thayer’s Approach.

Work was begun under cover of darkness on May 30. To avoid the fire of Confederate sharpshooters posted on higher ground along Fort Hill Ridge, members of the fatigue party had first to dig a tunnel through an exposed ridge line that separated the north and south prongs of Mint Spring Bayou. Once through the ridge, the men had to cross 150 yards of open ground before reaching the defiladed area at the base of Fort Hill Ridge. Klostermann had the men construct fascines made of cane that were placed across the top of the trench which served as a roof. This blindage was impervious to small arms fire and concealed the Federals as they moved to and from their work detail. 

By June 9, Klostermann’s sappers had dug their way up the slope to within 100 yards of the redoubt. To prevent the Federals from making a dash against their line, the Louisianans constructed a palisade of logs in front of their works. They also threw up an abatis of brush piles reinforced by wire entanglements. Despite these obstacles, the approach was driven up to the stockade of logs by July 3 and a gallery for a mine begun. The Confederates began a countermine of their own which they planned to charge with 100 pounds of powder. But the white flags that appeared along the line that afternoon put a stop to further digging, which denied Klostermann and the city’s defenders from completing their mines.  


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