The Battle of Fort Donelson was fought from February 11–16, 1862, in the Western Theater of the American Civil War. The Union capture of the Confederate fort near the Tennessee–Kentucky border opened the Cumberland River, an important avenue for the invasion of the South. The Union's success also elevated Brig. Gen. Ulysses S. Grant from an obscure and largely unproven leader to the rank of major general, and earned him the nickname of "Unconditional Surrender" Grant.
Following his capture of Fort Henry on February 6, Grant moved his army (later to become the Union's Army of the Tennessee) 12 miles (19 km) overland to Fort Donelson, from February 11 to 13, and conducted several small probing attacks. On February 14, Union gunboats under Flag Officer Andrew H. Foote attempted to reduce the fort with gunfire, but were forced to withdraw after sustaining heavy damage from the fort's water batteries.
On February 15, with the fort surrounded, the Confederates, commanded by Brig. Gen. John B. Floyd, launched a surprise attack, led by his second-in-command, Brig. Gen. Gideon Johnson Pillow, against the right flank of Grant's army. The intention was to open an escape route for retreat to Nashville, Tennessee. Grant was away from the battlefield at the start of the attack, but arrived to rally his men and counterattack. Pillow's attack succeeded in opening the route, but Floyd lost his nerve and ordered his men back to the fort. The following morning, Floyd and Pillow escaped with a small detachment of troops, relinquishing command to Brig. Gen. Simon Bolivar Buckner, who accepted Grant's demand of unconditional surrender later that evening. The battle resulted in virtually all of Kentucky as well as much of Tennessee, including Nashville, falling under Union control.
Background
Military situation
The battle of Fort Donelson, which began on February 12, took place shortly after the surrender of Fort Henry, Tennessee, on February 6, 1862. Fort Henry had been a key position in the center of a line defending Tennessee, and the capture of the fort now opened the Tennessee River to Union troop and supply movements. About 2,500 of Fort Henry's Confederate defenders escaped before its surrender by marching the 12 miles (19 km) east to Fort Donelson. In the days following the surrender at Fort Henry, Union troops cut the railroad lines south of the fort, restricting the Confederates' lateral mobility to move reinforcements into the area to defend against the larger Union forces.
With the surrender of Fort Henry, the Confederates faced some difficult choices. Grant's army now divided Confederate Gen. Albert Sidney Johnston's two main forces: Major General Leonidas Polk at Columbus, Kentucky, with 12,000 men, and William J. Hardee at Bowling Green, Kentucky, with 14,000 men. Fort Donelson had only about 5,000 men but Floyd and Buckner were moving their 8,000 troops from Russellville, Kentucky, to Clarksville, Tennessee. Union forces might attack Columbus; they might attack Fort Donelson and thereby threaten Nashville, Tennessee; or Grant and Maj. Gen. Don Carlos Buell, who was quartered in Louisville with 45,000 men, might attack Johnston head-on, with Grant following behind Buell. Johnston discussed the situation with his second-in-command, General Pierre G.T. Beauregard, and Hardee at Beauregard's headquarters at Covington House in Bowling Green on February 7. The generals were apprehensive about the ease with which Union gunboats defeated Fort Henry (not comprehending that the rising waters of the Tennessee River played a crucial role by inundating the fort). They decided that Fort Donelson was untenable, and adopted a course of action that forfeited the initiative across most of the Confederate defensive line, tacitly admitting that their defensive strategy for Tennessee was a sham.
The Confederate garrison at Columbus would be evacuated southwards, the Central Kentucky Army withdrawn from Bowling Green to Nashville, and Floyd's troops responsible for the defense of the Cumberland River. Johnston wanted to give command of the district to Beauregard, who had performed ably at Bull Run, but the latter declined because of a throat ailment. Instead, the responsibility went to Floyd, who had just arrived following an unsuccessful assignment under Robert E. Lee in western Virginia. Floyd was a wanted man in the North for alleged graft and secessionist activities when he was Secretary of War in the James Buchanan administration. Floyd's background was political, not military, but he was nevertheless the senior brigadier general on the Cumberland River.
On the Union side, Maj. Gen. Henry W. Halleck, Grant's superior as commander of the Department of the Missouri, was also apprehensive. Halleck had authorized Grant to capture Fort Henry, but now he felt that continuing to Fort Donelson was risky. Despite Grant's success to date, Halleck had little confidence in him, considering Grant to be reckless. Halleck attempted to convince his own rival, Don Carlos Buell, to take command of the campaign to get his additional forces engaged. Despite Johnston's high regard for Buell, the Union general was as passive as Grant was aggressive. Grant never suspected his superiors were considering relieving him, but he was well aware that any delay or reversal might be an opportunity for Halleck to lose his nerve and cancel the operation.
On February 6, Grant wired Halleck: "Fort Henry is ours. ... I shall take and destroy Fort Donelson on the 8th and return to Fort Henry." This self-imposed deadline was overly optimistic due to three factors: miserable road conditions on the twelve-mile march to Donelson, the need for troops to carry supplies away from the rising flood waters (by February 8, Fort Henry was completely submerged), and the damage that had been sustained by Foote's Western Gunboat Flotilla in the artillery duel at Fort Henry. If Grant had been able to move quickly, he might have taken Fort Donelson on February 8. Early in the morning of February 11, Grant held a council of war in which all of his generals supported his plans for an attack on Fort Donelson, with the exception of Brig. Gen. John A. McClernand, who had some reservations. This council in early 1862 was the last one that Grant held for the remainder of the Civil War.
After deciding that Fort Donelson was untenable on February 7, 1862, Johnston received intelligence from Buckner the next day reporting that Grant's army only numbered 12,000 men. In the next few days, Johnston received information from several officers describing the "considerable damage suffered by the Union ironclads during the battle of Fort Henry." These two pieces of information gave Johnston confidence that Fort Donelson could be defended. On February 12, Maj. Gen Braxton Bragg informed a subordinate that "General A.S. Johnston, from whom I heard yesterday, feels confident of holding Fort Donelson and driving the enemy from the Tennessee soon." Johnston ordered Floyd to concentrate his troops at Fort Donelson, confident that the 16,000 Confederate troops could defeat Grant's army and that Fort Donelson's batteries could repel the gunboats.
Opposing forces
Union
Grant's Union Army of the Tennessee of the District of Cairo consisted of three divisions, commanded by Brig. Gens. McClernand, C.F. Smith, and Lew Wallace. (At the start of the attack on Fort Donelson, Wallace was a brigade commander in reserve at Fort Henry, but was summoned on February 14 and charged with assembling a new division that included reinforcements arriving by steamship, including Charles Cruft's brigade on loan from Buell.) Two regiments of cavalry and eight batteries of artillery supported the infantry divisions. Altogether, the Union forces numbered nearly 25,000 men, although at the start of the battle, only 15,000 were available.
The Western Gunboat Flotilla under Flag Officer Andrew H. Foote consisted of four ironclad gunboats (flagship USS St. Louis, USS Carondelet, USS Louisville, and USS Pittsburg) and three timberclad (wooden) gunboats (USS Conestoga, USS Tyler, and USS Lexington). USS Essex and USS Cincinnati had been damaged at Fort Henry and were being repaired.
Confederate
Floyd's Confederate force of approximately 16,171 men consisted of three divisions of the Central Kentucky Army, garrison troops, and attached cavalry. The three divisions were commanded by Floyd (replaced by Colonel Gabriel C. Wharton when Floyd took command of the entire force) and Brig. Gens. Bushrod Johnson and Simon Bolivar Buckner. During the battle, Johnson, the engineering officer who briefly commanded Fort Donelson in late January, was effectively superseded by Brig. Gen. Gideon J. Pillow (Grant's opponent at his first battle at Belmont). Pillow, who arrived at Fort Donelson on February 9, was displaced from overall command of the fort when the more-senior Floyd arrived. The garrison troops were commanded by Col. John W. Head and the cavalry by Col. Nathan Bedford Forrest.
Fort Donelson was named for Brig. Gen. Daniel S. Donelson, who selected its site and began construction in 1861. It was considerably more formidable than Fort Henry. Fort Donelson rose about 100 feet (30 m) on approximately 100 acres of dry ground above the Cumberland River, which allowed for plunging fire against attacking gunboats, an advantage Fort Henry did not enjoy. The river batteries included twelve guns: ten 32-pounder smoothbore cannons, two 9-pounder smoothbore cannons, an 8-inch howitzer, a 6.5-inch rifle (128-pounder), and a 10-inch Columbiad. There were three miles (5 km) of trenches in a semicircle around the fort and the small town of Dover. The outer works were bounded by Hickman Creek to the west, Lick Creek to the east, and the Cumberland River to the north. These trenches, located on a commanding ridge and fronted by a dense abatis of cut trees and limbs stuck into the ground and pointing outward, were backed up by artillery and manned by Buckner and his Bowling Green troops on the right (with his flank anchored on Hickman Creek), and Johnson/Pillow on the left (with his flank near the Cumberland River). Facing the Confederates, from left to right, were Smith, Lew Wallace (who arrived on February 14), and McClernand. McClernand's right flank, which faced Pillow, had insufficient men to reach overflowing Lick Creek, so it was left unanchored. Through the center of the Confederate line ran the marshy Indian Creek, this point defended primarily by artillery overlooking it on each side.
Battle
Preliminary movements and attacks (February 12–13)
On February 12, most of the Union troops departed Fort Henry, where they were waiting for the return of Union gunboats and the arrival of additional troops that would increase the Union forces to about 25,000 men. The Union forces proceeded about 5 miles (8 km) on the two main roads leading between the two forts. They were delayed most of the day by a cavalry screen commanded by Nathan Bedford Forrest. Forrest's troops, sent out by Buckner, spotted a detachment from McClernand's division and opened fire against them. A brief skirmish ensued until orders from Buckner arrived to fall back within the entrenchments. After this withdrawal of Forrest's cavalry, the Union troops moved closer to the Confederate defense line while trying to cover any possible Confederate escape routes. McClernand's division made up the right of Grant's army with C.F. Smith's division forming the left. USS Carondelet was the first gunboat to arrive up the river, and she promptly fired numerous shells into the fort, testing its defenses before retiring. Grant arrived on February 12 and established his headquarters near the left side of the front of the line, at the Widow Crisp's house.
On February 11, Buckner relayed orders to Pillow from Floyd to release Floyd's and Buckner's troops to operate south of the river, near Cumberland City, where they would be able to attack the Union supply lines while keeping a clear path back to Nashville. However, this would leave the Confederate forces at Fort Donelson heavily outnumbered. Gen. Pillow left early on the morning of February 12 to argue these orders with Gen. Floyd himself leaving Buckner in charge of the fort. After hearing sounds of artillery fire, Pillow returned to Fort Donelson to resume command. After the events of the day, Buckner remained at Fort Donelson to command the Confederate right. With the arrival of Grant's army, General Johnston ordered Floyd to take any troops remaining in Clarksville to aid in the defense of Fort Donelson.