In early April 1862, Ulysses S. Grant's Army of the Tennessee — some 42,000 men — encamped at Pittsburg Landing on the Tennessee River, awaiting Don Carlos Buell's Army of the Ohio before advancing on the Confederate rail junction at Corinth, Mississippi. Grant's army was spread across miles of wooded Tennessee terrain, largely unsuspecting of danger.

Confederate commander Albert Sidney Johnston had secretly concentrated 44,968 men at Corinth. On the night of April 5–6, four corps under Hardee, Bragg, Polk, and Breckinridge moved silently into assault positions. Just after dawn, Confederate skirmishers collided with a Federal patrol near Fraley Field. By 6 AM, the main assault was rolling.

Sherman's division broke after fierce resistance; Prentiss's collapsed almost immediately. But a Federal line anchored in a sunken lane — the Hornet's Nest — held off repeated Confederate charges for six hours. Johnston was killed near the Peach Orchard at approximately 2:30 PM. By 5:30 PM, Prentiss surrendered with 2,200 men. Grant's final line held along Dill Branch ravine, supported by gunboat fire.

The fighting left its name on the ground itself. The battle takes its name from Shiloh Church, the small log meeting house near Sherman's headquarters. As his line gave way it fell back through Review Field. In front of the sunken road, Duncan Field became a killing ground where Ruggles massed 62 guns. Wounded men from both sides crawled to drink at Bloody Pond, whose water ran red.

The battlefield was framed by its roads, and they shaped how the fighting moved. Two roads tied Pittsburg Landing to the Confederate base at Corinth: the main Corinth Road, running southwest past Shiloh Church, and the Eastern Corinth Road, which dropped south through the center of the field past the sunken lane. Crossing them east–west was the Hamburg-Purdy Road, tracing much of the morning's front, while the Hamburg-Savannah Road (River Road) ran north–south along the river side, anchoring the Union left. Where the Corinth Road met the Hamburg-Purdy Road, just northeast of Shiloh Church, sat the Crossroads — the field's key junction, which Beauregard used as his headquarters through the afternoon of April 6. Click any road to trace it on the map.

During the night, Buell's Army of the Ohio crossed at Pittsburg Landing with ~20,000 fresh troops. At dawn on April 7, Grant ordered a general advance. Lew Wallace's division opened the counterattack across Jones Field on the Union right, while some of the last fighting raged near Water Oaks Pond. The exhausted Confederates were steadily pushed back; by early afternoon Beauregard ordered a withdrawal to Corinth.

The battle cost approximately 23,750 casualties — more than all previous American wars combined. It shattered any illusion of a short war and signaled the grim nature of the conflict to come.