The battle Hostile_encounter was fought Hostile_encounter between the Army of the Cumberland under Maj. Gen. William Rosecrans and the Confederate Army of Tennessee under Gen. Braxton Bragg , and was named Name_conferral for Chickamauga Creek , which meanders near the battle Hostile_encounter area in northwest Georgia ( and ultimately flows Motion into the Tennessee River about 3.5 miles ( 5.6 km ) northeast of downtown Chattanooga ) .

After his successful Tullahoma Campaign Military_operation , Rosecrans renewed Recovering the offensive , aiming Aiming to force Causation the Confederates out of Chattanooga .

In early September , Rosecrans consolidated Cause_change_of_strength his forces Causation scattered Dispersal in Tennessee and Georgia and forced Causation Bragg 's army out of Chattanooga , heading Self_motion south .

Bragg was determined Deciding to reoccupy Conquering Chattanooga and decided Deciding to meet Come_together a part of Rosecrans 's army , defeat Conquering it , and then move back Self_motion into the city .

In late morning , Rosecrans was misinformed Coming_to_believe that he had a gap in his line .

In moving Motion units to shore up the supposed gap , Rosecrans accidentally created Creating an actual gap , directly in the path of an eight-brigade assault Attack on a narrow front by Confederate Lt. Gen. James Longstreet , whose corps had been detached Removing from the Army of Northern Virginia .

In the resulting rout , Longstreet 's attack Attack drove Motion one-third of the Union army , including Rosecrans himself , from the field .

Union Maj. Gen. William S. Rosecrans 's Army of the Cumberland marched Self_motion from Nashville , Tennessee , on December 26 , 1862 , to challenge Confronting_problem General Braxton Bragg 's Army of Tennessee at Murfreesboro .

Falsely believing that Rosecrans was receiving Receiving reinforcements Cause_change_of_strength , Bragg chose Choosing to withdraw Escaping his army on January 3 to Tullahoma , Tennessee .