Union Maj. Gen. William Tecumseh Sherman invaded Georgia from the vicinity of Chattanooga, Tennessee, beginning in May 1864, opposed by the Confederate general Joseph E. Johnston.

In July, the Confederate president, Jefferson Davis, replaced Johnston with the more aggressive General John Bell Hood, who began challenging the Union Army in a series of costly frontal assaults.

Hood's army was eventually besieged in Atlanta and the city fell on September 2, setting the stage for Sherman's March to the Sea and hastening the end of the war.

While he, George G. Meade, Benjamin Butler, Franz Sigel, George Crook, and William W. Averell advanced in Virginia against Robert E. Lee, and Nathaniel Banks attempted to capture Mobile, Alabama, Sherman was assigned the mission of defeating Johnston's army, capturing Atlanta, and striking through Georgia and the Confederate heartland.

Sherman prudently avoided suicidal frontal assaults against most of these positions, instead maneuvering in flanking marches around the defenses as he advanced from Chattanooga towards Atlanta.

Sherman had earlier decided to demonstrate against the strong Confederate position with the bulk of his force while he sent a smaller portion through Snake Creek Gap, to the right, to hit the Western & Atlantic Railroad at Resaca, Georgia.

In the meantime, the third column, under McPherson, passed unnoticed through Snake Creek Gap and on May 9 advanced to the outskirts of Resaca, where it found a small Confederate force entrenched.

Fearing defeat, McPherson pulled his column back to Snake Creek Gap, which Sherman's orders gave him authority to do.

The next morning, as he discovered Sherman's army withdrawing from their positions in front of Rocky Face Ridge, Johnston retired south towards Resaca.

Full scale fighting occurred on May 14, and the Union troops were generally repulsed except on Johnston's right flank, where Sherman did not fully exploit his advantage.

On May 15, the battle continued with no advantage to either side until Sherman sent a force across the Oostanaula River at Lay's Ferry, towards Johnston's railroad supply line.

Failing to find a good defensive position south of Calhoun, Johnston continued to Adairsville while the Confederate cavalry fought a skillful rearguard action.

Sherman continued looking for a way around Johnston's line, and on June 1, his cavalry occupied Allatoona Pass, which had a railroad and would allow his men and supplies to reach him by train.

On June 14, Lt. Gen. Leonidas Polk was killed by an artillery shell while scouting enemy positions with Hardee and Johnston and was temporarily replaced by Maj. Gen. William W. Loring.

Sherman made some unsuccessful attacks on this position but eventually extended the line on his right and forced Johnston to withdraw from the Marietta area on July 2–3.

[15] Having encountered entrenched Confederates astride Kennesaw Mountain stretching southward, Sherman fixed them in front and extended his right wing to envelop their flank and menace the railroad.

[16] This battle was a notable exception to Sherman's policy in the campaign of avoiding frontal assaults and moving around the enemy's left flank.

Johnston decided to attack Thomas as he crossed the creek, but Confederate President Jefferson Davis relieved him of command and appointed Hood to take his place.

The advance of McPherson from the east side of Atlanta distracted Hood from his offensive and drew off Confederate troops that might have joined the attack on Thomas.

In the meantime, he sent William J. Hardee with his corps on a fifteen-mile (24 km) march to hit the unprotected Union left and rear, east of the city.

He ordered Howard's Army of the Tennessee to move from the left wing to the right and cut Hood's last railroad supply line between East Point and Atlanta.

Hood foresaw such a maneuver and sent the two corps of Lt. Gen. Stephen D. Lee and Lt. Gen. Alexander P. Stewart to intercept and destroy the Union force at Ezra Church.

Concurrent attempts by two columns of Union cavalry to cut the railroads south of Atlanta ended in failure, with one division under Maj. Gen. Edward M. McCook completely smashed at the Battle of Brown's Mill and the other force also repulsed and its commander, Maj. Gen. George Stoneman, taken prisoner.

Greatly outnumbered, the Union garrison retired to fortifications on a hill outside the town where they successfully held out, although the attack continued until after midnight.

Leaving on August 18, Kilpatrick hit the Atlanta & West Point Railroad that evening, tearing up a small area of tracks.

Confederate infantry (Patrick Cleburne's Division) appeared and the raiders were forced to fight into the night, finally fleeing to prevent encirclement.

Sherman had successfully cut Hood's supply lines in the past by sending out detachments of cavalry, but the Confederates quickly repaired the damage.

To counter the move, Hood sent Hardee with two corps to halt and possibly rout the Union troops, not realizing Sherman's army was there in force.

[25] On the night of September 1, Hood evacuated Atlanta and ordered that the 81 rail cars filled with ammunition and other military supplies be destroyed.

However, the capture of Atlanta made an enormous contribution to Union morale and was an important factor in the re-election of President Abraham Lincoln.