Chattanooga campaign

The Chattanooga campaign was a series of maneuvers and battles in October and November 1863, during the American Civil War. Following the defeat of Maj. Gen. William S. Rosecrans's Union Army of the Cumberland at the Battle of Chickamauga in September, the Confederate Army of Tennessee under Gen. Braxton Bragg besieged Rosecrans and his men by occupying key high terrain around Chattanooga, Tennessee. Maj. Gen. Ulysses S. Grant was given command of Union forces in the West which was now consolidated under the Division of the Mississippi. Significant reinforcements also began to arrive with him in Chattanooga from Mississippi and the Eastern Theater. On October 18, Grant removed Rosecrans from command of the Army of the Cumberland and replaced him with Major General George Henry Thomas.

During the opening of a supply line (the "Cracker Line") to feed the starving men and animals in Chattanooga, a force under Maj. Gen. Joseph Hooker fought off a Confederate counterattack at the Battle of Wauhatchie on October 28–29, 1863. On November 23, the Army of the Cumberland advanced from the fortifications around Chattanooga to seize the strategic high ground at Orchard Knob while elements of the Union Army of the Tennessee under Maj. Gen. William Tecumseh Sherman maneuvered to launch a surprise attack against Bragg's right flank on Missionary Ridge. On November 24, Sherman's men crossed the Tennessee River in the morning and then advanced to occupy high ground at the northern end of Missionary Ridge in the afternoon. The same day, a mixed force of almost three divisions under Maj. Gen. Joseph Hooker defeated the Confederates in the Battle of Lookout Mountain. The next day they began a movement toward Bragg's left flank at Rossville.

On November 25, Sherman's attack on Bragg's right flank made little progress. To distract Bragg’s attention, Grant ordered Thomas’s army to advance through the center and seize the Confederate positions at the base of Missionary Ridge. The untenability of these newly captured entrenchments caused Thomas's men to surge to the top of Missionary Ridge and, with the help of Hooker's force advancing north from Rossville, routed the Confederate Army of Tennessee. The Confederates retreated to Dalton, Georgia, successfully fighting off the Union pursuit at the Battle of Ringgold Gap. Bragg's defeat eliminated the last significant Confederate control of Tennessee and opened the door to an invasion of the Deep South, leading to Sherman's Atlanta campaign of 1864.

Chattanooga was a vital rail hub (with lines going north toward Nashville and Knoxville and south toward Atlanta), and an important manufacturing center for the production of iron and coal, located on the navigable Tennessee River. In September 1863, the Union Army of the Cumberland under Maj. Gen. William S. Rosecrans executed a series of maneuvers that forced Confederate Gen. Braxton Bragg and his Army of Tennessee to abandon Chattanooga and withdraw into northern Georgia. Rosecrans pursued Bragg and the two armies collided at the Battle of Chickamauga on September 19–20. Bragg achieved a major victory when a gap was opened mistakenly in the Union line and a strong assaulting force commanded by Lt. Gen. James Longstreet serendipitously drove through it and routed a good portion of the Union army. A determined defensive stand by Maj. Gen. George H. Thomas on Snodgrass Hill saved the army from total destruction, earning him the nickname "Rock of Chickamauga" and allowing time for most of Rosecrans's army to retreat to Chattanooga. Bragg failed to cut off the escape routes to Chattanooga or organize a pursuit that could have seriously damaged the Union army before it regrouped and fortified the city’s defenses. The Union forces took advantage of previous Confederate works to erect strong defensive positions in a tight, 3-mile-long semicircle around the city.

Bragg had three courses of action. The Union forces repurposed existing Confederate fortifications to build strong defensive positions, forming a tight, three-mile-long semicircle around the city. The flanking option was deemed to be impracticable because Bragg's army was short on ammunition, they had no pontoons for river crossing, and Longstreet's corps from Virginia had arrived at Chickamauga without wagons. A direct assault was too costly against a well-fortified enemy. Receiving intelligence that Rosecrans's men had only six days of rations, Bragg chose the siege option, while attempting to accumulate sufficient logistical capability to cross the Tennessee.

Bragg's army besieged the city, threatening to starve the Union forces into surrender. The Confederates established themselves on Missionary Ridge and Lookout Mountain, both of which had excellent views of the city, the Tennessee River flowing north of the city, and the Union's supply lines. Bragg also had little inclination to take offensive action against the Federal army because he was occupied in leadership quarrels within his army. On September 29, Bragg relieved from command two of his subordinates who had disappointed him in the Chickamauga campaign: Maj. Gen. Thomas C. Hindman (who had failed to destroy part of the Union army at McLemore's Cove) and Lt. Gen. Leonidas Polk (who had delayed attacking on September 20 at Chickamauga). On October 4, twelve of his most senior generals sent a petition to Confederate President Jefferson Davis, demanding that Bragg be relieved of command. Davis personally visited Chattanooga to hear the complaints. After he decided to retain Bragg in command, Bragg retaliated against some of those generals by relieving Lt. Gen. D.H. Hill and Maj. Gen. Simon B. Buckner.

Never in the history of the Army of the Cumberland had the spirit of its officers and men been more depressed. The battle of Chickamauga had not only been fought and lost, but we also lost what was more than losing the battle. We had lost confidence in our commander.

In Chattanooga, Rosecrans was stunned by the defeat of his army and became psychologically unable to take decisive action to lift the siege. President Abraham Lincoln remarked that Rosecrans seemed "confused and stunned like a duck hit on the head." Union soldiers began to feel the effect of extremely short rations and many of their horses and mules died. The only supply line that was not controlled by the Confederates was a roundabout, tortuous course nearly 60 miles long over Walden's Ridge from Bridgeport, Alabama. Heavy rains began to fall in late September, washing away long stretches of the mountain roads. On October 1, Maj. Gen. Joseph Wheeler's Confederate cavalry intercepted and severely damaged a train of 800 wagons—burning hundreds of the wagons, and shooting or sabering hundreds of mules—at the start of his October 1863 Raid through Tennessee to sever Rosecrans's supply line. Toward the end of October, typical Federal soldiers' rations were "four cakes of hard bread and a quarter pound of pork" every three days.