"By mid-February 1862, United States forces had won decisive victories in the West at Mill Springs, Kentucky, and Forts Henry and Donelson in Tennessee. These successes opened the way for invasion up the Tennessee River to sever Confederate rail communications along the important Memphis & Charleston and Mobile & Ohio railroads. Forced to abandon Kentucky and Middle Tennessee, Gen. Albert Sidney Johnston, supreme Confederate commander in the West, moved to protect his rail communications by concentrating his scattered forces around the small town of Corinth in northeast Mississippi—strategic crossroads of the Memphis & Charleston and the Mobile & Ohio.
In March, Maj. Gen. Henry W. Halleck, commanding U.S. forces in the West, advanced armies under Maj. Gens. Ulysses S. Grant and Don Carlos Buell southward to sever the Southern railroads. Grant ascended the Tennessee River by steamboat, disembarking his Army of the Tennessee at Pittsburg Landing, 22 miles northeast of Corinth. There he established a base of operations on a plateau west of the river, with his forward camps posted two miles inland around a log church called Shiloh Meeting House. Halleck had specifically instructed Grant not to engage the Confederates until he had been reinforced by Buell's Army of the Ohio, then marching overland from Nashville. Once combined, the two armies would advance on Corinth and permanently break western Confederate railroad communications.
General Johnston, aware of Federal designs on Corinth, planned to smash Grant's army at Pittsburg Landing before Buell arrived. He placed his troops in motion on April 3, but heavy rain and difficulties encountered by marching large columns of men, artillery, and heavy wagons over muddy roads, delayed the attack. By nightfall, April 5, his Army of the Mississippi, nearly 44,000 men present for duty, was finally deployed for battle four miles southwest of Pittsburg Landing.
At daybreak, Sunday, April 6, the Confederates stormed out of the woods and assailed the forward Federal camps around Shiloh Church. Grant and his nearly 40,000 men present for duty were equally surprised by the onslaught. The Federals soon rallied, however, and bitter fighting consumed “Shiloh Hill.” Throughout the morning, Confederate brigades slowly gained ground, forcing Grant's troops to give way, grudgingly, to fight a succession of defensive stands at Shiloh Church, the Peach Orchard, Water Oaks Pond, and within an impenetrable oak thicket battle survivors named the Hornets' Nest.
Despite having achieved surprise, Johnston's troops soon became as disorganized as the Federals. The Southern attack lost coordination as corps, divisions, and brigades became entangled. Then, at mid-afternoon, as he supervised an assault on the Union left, Johnston was struck in the right leg by a stray bullet and bled to death, leaving Gen. P.G.T. Beauregard in command of the Confederate army. Grant's battered divisions retired to a strong position extending west from Pittsburg Landing where massed artillery and rugged ravines protected their front and flanks. Fighting ended at nightfall.
Overnight, reinforcements from Buell's army reached Pittsburg Landing. Beauregard, unaware Buell had arrived, planned to finish the destruction of Grant the next day. At dawn, April 7, however, it was Grant who attacked. Throughout the day, the combined Union armies, numbering over 54,500 men, hammered Beauregard's depleted ranks, now mustering barely 34,000 troops. Despite mounting desperate counterattacks, the exhausted Confederates could not stem the increasingly stronger Federal tide. Forced back to Shiloh Church, Beauregard skillfully withdrew his outnumbered command and returned to Corinth. The battered Federals did not press the pursuit. The battle of Shiloh, or Pittsburg Landing, was over. It had cost both sides a combined total of 23,746 men killed, wounded, or missing, and ultimate control of Corinth’s railroad junction remained in doubt.
Halleck, recognizing Corinth’s military value, considered its capture more important than the destruction of Confederate armies. Reinforced by another army under Gen. John Pope, he cautiously advanced southward from Tennessee and, by late May, entrenched his three armies within cannon range of Confederate fortifications defending the strategic crossroads. Despite being reinforced by Maj. Gen. Earl Van Dorn’s Trans-Mississippi Army, Beauregard withdrew south to Tupelo, abandoning the most viable line of east-west rail communications in the western Confederacy.
Federal efforts to recover the Mississippi Valley stalled in the late summer of 1862, and Confederate leaders launched counteroffensives in every theater. Armies led by Gens. Braxton Bragg and Edmund Kirby Smith invaded Kentucky, while troops under Van Dorn boldly attacked the heavily fortified Union garrison at Corinth, “linchpin” of Federal control in northern Mississippi. In one of the more bitterly contested battles of the war, Van Dorn was decisively repulsed, following two days of carnage (October 3-4) that claimed nearly 7,000 more Confederate and Union casualties.
Although overshadowed by the failure of Robert E. Lee's Confederate invasion in Maryland, Van Dorn's defeat, coupled with Bragg's retreat from Kentucky after the battle of Perryville (October 8), caused discouragement in Richmond and relief in Washington. More significantly, Van Dorn's defeat at Corinth—the last Confederate offensive in Mississippi—seriously weakened the only mobile Southern army defending the Mississippi Valley. This permitted Ulysses S. Grant to launch a relentless nine-month campaign to capture “the fortress city” of Vicksburg and recover the Mississippi River."