Following fall of Forts Henry and Donelson in February of 1862, the commander of Confederate forces in the West, Gen. Albert Sidney Johnston, was compelled to withdraw from Kentucky, and leave much of western and middle Tennessee to the Federals. To prepare for future offensive operations, Johnston marshalled his forces at Corinth, Mississippi—a major transportation center. The Confederate retreat was a welcome surprise to Union commander Maj. Gen. Ulysses S. Grant, whose Army of the Tennessee would need time to prepare for its own offensive along the Tennessee river. Grant's army made camp at Pittsburg Landing where it spent time drilling raw recruits and awaiting reinforcements in the form of Maj. Gen. Don Carlos Buell’s Army of the Ohio. Johnston needed to strike Grant at Pittsburg Landing before the two Federal armies could unite.
Aware of Grant's location and strength—and that more Yankees were on the way—Johnston originally planned to attack the unfortified Union position on April 4, but weather and other logistical concerns delayed the attack until April 6. The Confederate's morning assault completely surprised and routed many of the unprepared Northerners. By afternoon, the a few stalwart bands of Federals established a battle line along a sunken road, known as the “Hornets Nest.” After repeated attempts to carry the position, the Rebels pounded the Yankees with massed artillery, and ultimately surrounded them. Later in the day Federals established a defensive line covering Pittsburg Landing, anchored with artillery and augmented by Buell’s men, who had begun to arrive. Fighting continued until after dark, but the Federals held. Though they had successfully driven the Yankees back, there was, however, one significant blow to the Confederate cause on April 6. Johnston had been mortally wounded early during the day and command of the Confederate force fell to Gen. P.G.T. Beauregard.
With the addition of Buell's men, the Federal force of around 40,000 outnumbered Beauregard’s army of fewer than 30,000. Beauregard, however, was unaware of Buell’s arrival. Therefore, when William Nelson’s division of Buell’s army launched an attack at 6:00 am on April 7, Beauregard immediately ordered a counterattack. Though Beauregard's counter thrust was initially successful, Union resistance stiffened and the Confederates were compelled to fall back and regroup. Beauregard ordered a second counterattack, which halted the Federals' advance but ultimately ended in stalemate. By this point, Beauregard realized he was outnumbered and, having already suffered tremendous casualties, broke contact with the Yankees to began a retreat to Corinth.