Following the fall of Forts Henry and Donelson, Confederate General Albert S. Johnston was compelled to withdraw from Kentucky, and leave much of western and middle Tennessee to the Federals. Major General Don Carlos Buell and his Army of the Ohio sliced into Middle Tennessee, capturing Nashville on February 25—the first Confederate state capital to fall—while Major General Ulysses S. Grant’s Army of the Tennessee drove south toward Mississippi. Federal armies severed Confederate railroads, preventing reinforcements between the rebel armies in Virginia and those in the west, effectively splitting the Confederacy in two.
Johnston marshaled his forces at Corinth, Mississippi, a major railroad junction where the east-west rail lines met. Meantime, Grant prepared his army for its own offensive and camped at Pittsburg Landing 22 miles north of Corinth, where it spent time drilling recruits and awaiting the arrival of Buell’s army.
Johnston and his 44,000-man Army of Mississippi anticipated a Federal move against Corinth. Johnston planned to smash Grant's army at Pittsburg Landing before Buell could join him. Johnston placed his troops in motion on April 3 but heavy rains delayed his attack. By nightfall on April 5, his army was deployed for battle only four miles southwest of Pittsburg Landing, and pickets from both sides nervously exchanged gunfire in the dense woods that evening.
At daybreak on Sunday, April 6, three corps of Confederate infantry stormed out of the woods and swept into the southernmost Federal camps of Brig. Gen. Benjamin M. Prentiss’ division. Most of the men were unprepared for the onslaught. Brigadier General William T. Sherman, the senior division commander at Pittsburg Landing while Grant was downriver at his headquarters, had dismissed reports warning of a Confederates advance, refusing to believe that Johnston would leave Corinth. Soon, the nearby divisions of generals McClernand and Stephen Hurlbut were also hard pressed by the rebel attack. Intense fighting swirled around Shiloh Church as the Confederates swept Sherman’s line from that area. Sherman's men counterattacked but slowly lost ground and fell back northeast toward Pittsburg Landing.
Near the center of the Union line was a thick grove of oak trees and dense underbrush bordered by a farm lane. During the morning, this was the scene of the most intense fighting of the battle. For six hours, Confederate brigades charged into Union defenders. Each assault was shattered by a storm of Federal musketry and artillery. Confederate survivors labeled the position “a hornets’ nest.” On the northwest edge of the field, Rebel division commander Brig. Gen. Daniel Ruggles assembled 62 artillery pieces to blast the Union line barely 400 yards away. “Ruggles’ Battery” was the largest assembly of artillery in the war up to that time. After multiple attacks, the Confederates surrounded the position and forced nearly 2,300 Yankees to surrender, including Prentiss.
Around 2:30 p.m., while leading an attack on the left end of the Hornets’ Nest line, Johnston was shot behind the right knee as he rode ahead of his troops. The bullet severed an artery, and blood poured into his boot unseen by those around him. His staff laid Johnston on the ground under a tree, where he bled to death within minutes. Johnston’s second-in-command, Gen. P.G.T. Beauregard, took charge, calling a halt to the assaults.
On the night of April 5, the first units of Buell’s army arrived. Grant ordered the establishment of a new defensive line bolstered with more than 50 pieces of heavy artillery. Undaunted by the day’s events, Grant formed plans to go on the offensive the next morning. Aware he had been caught unprepared during the morning attack, Sherman remarked, “Well, Grant, we've had the devil's own day, haven't we?” Grant, unmoved, drew from his cigar and proclaimed, “Yes. Lick em tomorrow, though.”
Grant attacked at 6:00 a.m. on April 7. Beauregard immediately ordered a counterattack. Though his force was initially successful, Union resistance stiffened, and the Confederates were compelled to fall back. Around 3:00 p.m., Beauregard broke contact with the Yankees and retreated toward Corinth.
The carnage was unprecedented with some 23,800 casualties—more casualties than the Revolution, War of 1812 and Mexican War combined.
The Confederate defeat at Shiloh ended any hopes of blocking the Union advance into Mississippi, and the Federals set their sights on the railroad crossroads of Corinth.