In June and early July of 1863 Union General William Rosecrans had outmaneuvered Confederate General Braxton Bragg in middle Tennessee during the Tullahoma Campaign, driving the Confederates from Middle Tennessee.
However, Rosecrans then halted, despite urgings from the War Department, while he considered pursuing the Confederates into mountainous territory. Rosecrans explained his delay, citing ripening crops to be harvested, repair of railroads, and his need for support for both flanks of his army.
On Sunday, August 16, 1863 Rosecrans resumed his offensive against Bragg’s Confederates, moving the Union Army of the Cumberland from south of Tullahoma toward the Tennessee River and Chattanooga in the start of the Chickamauga Campaign. Bragg and his Army of Tennessee quickly called on the national Confederate government for more troops and supplies.