Union Siege Operations
The Union siege of Vicksburg (Video) lasted for 47 days. As Grant’s army tightened the siege, conditions inside the city became intolerable for the Confederate troops and the civilians alike.
On the siege lines, the Union troops began almost immediately to dig thirteen approaches or saps toward the Confederate defenses. This became the focus of Union operations for the next six weeks. As monotonous and unexciting as this activity was, it became the key to the Union victory at Vicksburg.
One of the primary engineering officers on the Union side was Captain Andrew Hickenlooper, chief engineer for Maj. Gen. James McPherson’s 17th Corps. Hickenlooper was a meticulous engineer who examined the terrain carefully during the May 25th truce. He prepared a map of the area and from this he determined the best approach to the all-important Third Louisiana Redan. Hickenlooper had noticed that this key position jutted out from the Confederate defensive line and its capture would make the Confederate earthworks on either side indefensible. (Official Report)
Hickenlooper’s sap became known as Logan’s Approach after Maj. Gen. John Logan, the division commander in this stretch of the Union siege lines. The Union troops worked in three shifts of 100 men per shift, starting on May 26th. They began to dig about 150 feet southeast of the Shirley House and 400 yards east of their objective.
Typically, a sap was about 7 feet deep and 8 feet wide. This allowed a soldier to stand up in the sap without the fear of being shot and was wide enough for a column of four men to move down the trench. Because the excavated dirt was piled on either side, it effectively was 10 feet deep.
The sappers at Vicksburg worked around the clock with picks and shovels in the Mississippi heat and humidity. Excavation in the soft loess soil was easy and the sap was dug fairly quickly. By the end of the first day it was several hundred feet west of its starting point. The sappers were protected by sap-rollers, bundles of cane and vine, that were assembled and placed on the ground in front of the sappers.
The sap-rollers that was used at Logan’s approach was a railroad flatcar with wooden wheels and stacked with 20 cotton bales. The flatcar also served as a rolling firing platform, complete with firing loops for riflemen. Hickenlooper’s sappers had their own fire support.
After several days of digging, Hickenlooper reduced the number of men working on the approach by one-third. On June 3rd, the sap reached a commanding knoll overlooking the Third Louisiana Redan. Here, the Union forces dug a trench left and right along the crest of the ridge and established an artillery position.
They named it Battery Hickenlooper and installed 2-24-pound howitzers and 1-6-pound gun. The so-called breaching battery went into action on June 6th. Two weeks later 2-30-pound Parrott rifled guns were added and they soon created a breach in the redan. The Confederates tried to repair the breach at night but the attempts proved to be futile.
By the end of the siege, the Union army had 220 guns of all types pounding the Confederate defensive lines. The land-based guns were augmented by 13 heavy naval guns from Rear Admiral David Dixon Porter’s Mississippi River flotilla. These guns were manhandled up the bluffs and placed in batteries overlooking the river. The navy also used gunboats and mortar boats to keep up a constant bombardment of the Confederate positions.
Inside the city, Lt. Gen. John C. Pemberton’s Confederates could do little to counter the continual bombardment. It pulverized his defensive works and the city itself from every direction. The Confederates had 128 guns that they could use to counter the Union artillery. Most of these were light field pieces. The Confederates had lost a significant numbers of guns at the battle of Champion Hill.
When the Union sappers reached about 75 yards from the Third Louisiana Redan on June 8th, the Confederate defenders were able to shoot down into the approach. The troops of the 23rd Indiana Infantry countered by building a tower of railroad ties just behind Battery Hickenlooper. Called “Coonskin’s Tower” for Lt. Henry C. Foster, the Hoosiers were able to look into the parapets of the redan and keep the enemy from firing at the sappers. Despite being a ramshackle affair, the tower lasted throughout the siege. On one occasion, General Grant visited it to observe the enemy positions.
By June 16th, the head of the approach was within 25 yards of the Confederate defensive lines. Hickenlooper fortified it with two lines of rifle pits on either side of the approach, to protect it from Confederate attack. He also discontinued the night digging. Six days later, the approach reached the apex of the redan.
On June 23rd, Hickenlooper began a mine under the redan. He employed 35 experienced miners to excavate a chamber, called a gallery under the redan. The Confederates could hear the miners and frantically sank a countermine shaft. The Union miners finished the gallery on June 25th. The mine was packed with 2,200 pounds of black powder. With thousands of troops massed behind Battery Hickenlooper, the fuse was lit at 3:00 PM on June 25th.
Brig. Gen. Louis Hébert commanded the troops in the redan. As an experienced engineer, he knew what was coming and he ordered his men to withdraw from the apex of the redan. Pemberton also knew that the mine explosion would be followed by an infantry assault so he massed troops behind the position.
The explosion took place at 3:28 PM when there was a muffled thud and the ground erupted beneath the Confederate position. Dirt and flames shot into the air. According to one Illinois officer, the blast was “mingled with flashes of fire and clouds of smoke, through which could be occasionly be caught glimpses of dark objects-men, gun carriages, shelters and so on.” The blast tore a hole in the forward part of the redan 30 feet wide by 15 feet deep.
The ensuing battle lasted for several hours with both sides desperately attempting to hold the key position. Men used clubbed muskets, bayonets and fists against each other. As darkness approached, both sides continued to battle. Reinforcements poured in from both sides as the fighting continued throughout the night. As the morning of June 26th wore on, Grant, who was observing the attack, ordered McPherson to recall his men and dig in along the exterior slope of the redan.
Despite lasting more than 20 hours, casualties inside the redan were minimized by the small size of the position. The Union casualties were 34 killed and 209 wounded while the Confederates had 21 killed and 73 wounded.
Hickenlooper continued mining with a second explosion on July 1st which demolished more of the redan. There was no infantry assault after this explosion. Union pioneers continued to expand the sap for a future assault but Pemberton surrendered before it was needed.
Saps and mines were only a part of the Union siege operations at Vicksburg. The Union lines mirrored the Confederate defenses with a complex maze of approaches, battery positions, covered passageways and bombproofs. The Union Interior Line included more than 60,000 linear feet of excavations.
It prevented the Confederates from breaking out of the trap that Vicksburg was becoming while preventing supplies from reaching the city. The Union troops were able to move around the siege lines in relative safety. The constant work kept the troops busy while they waited for the Confederates to surrender. During the siege of Vicksburg ‘spades were trumps’ and Grant held all of the cards.