Bragg had not retreated to lick his wounds. He had retreated to gather strength and turn. Reinforced now by Longstreet’s corps coming from Virginia and by troops sent up from Mississippi, Bragg made the decision that set the trap: instead of falling back farther, he wheeled around to strike Rosecrans’s strung-out, separated columns south of Chattanooga, near a creek called West Chickamauga Creek. This would be the first major battle of the war fought on Georgia soil. The name comes down to us with a legend attached, that "Chickamauga" means "river of death," but that translation is folklore, not fact, and the older derivation runs through a Chickasaw word for something closer to "be good." The grim name is a story the war wrote onto the place afterward, not a Cherokee prophecy.

The ground itself shaped everything that happened here. West Chickamauga Creek ran roughly north to south, east of the main road. That road, the LaFayette Road, ran north to south too, and it was the spine of the whole battle: run it north and it took you toward Rossville and Chattanooga, the Union army’s lifeline. The Union line formed along and west of that road. But the country between the creek and the road was not open field. It was dense, choked forest grown back over old cleared land, so thick with young timber and brush that men could not see across it, could not control their own lines inside it, could not tell friend from enemy at any distance. Both armies would feed troops blindly into those trees. Commanders would lose track of where their own divisions were. This was a battle fought, for the most part, by men who could not see the battle.

It opened on September 18 at the creek crossings. Bragg’s Confederates pushed for the bridges over Chickamauga Creek so they could get across to the western side and fall on the Union army. Union cavalry and mounted infantry (foot soldiers who rode to the fight and dismounted to shoot) fought to delay them. The sharpest of those delaying fights belonged to Col. John T. Wilder (North), whose "Lightning Brigade" of mounted infantry carried Spencer repeating rifles, a weapon that loaded a tube of cartridges and fired round after round without stopping to reload between shots, giving a few men the firepower of many. Wilder’s brigade held Alexander’s Bridge; Col. Robert Minty’s horsemen held Reed’s Bridge to the north. The fighting on the 18th was minor, the curtain-raiser, but it told both sides the armies had found each other.

The real battle came on September 19, and it came as a confused, sprawling brawl spread across nearly four miles of forest. Neither commander could shape it. Both fed brigades in piecemeal, a few regiments at a time, wherever the firing flared up. Confederate attacks went in disjointed and uncoordinated, broken up by the very trees they were attacking through. Lines collided in the timber, fired blind, and lost cohesion almost as fast as they formed. The day closed with a twilight attack by Maj. Gen. Patrick Cleburne (South) near Winfrey field. When the firing died down, no one had won. But underneath the chaos, Rosecrans had been doing one thing steadily and deliberately all day: shifting the weight of his army northward, toward the LaFayette Road and Rossville, guarding the road back to Chattanooga that he could not afford to lose. That northward shift would matter enormously in the morning.

A full day of fighting across four miles of woods produced no decision and no clear winner, a bloody draw in the dark. But the day was not wasted on either side. Rosecrans used it to pull his army north to cover his retreat road, and Bragg used the night to bring up Longstreet and reorganize his whole army into two wings (each a cluster of corps under one commander) for a coordinated assault at dawn.