Sherman had 100,000 men in three parts, The Army of the Cumberland, The Army of Tennessee, and The Corps sized Army of the Ohio.. His orders from Grant were "to move against Johnston's army, to break it up, and to get into the interior of the enemy's country as far as you can, inflicting all the damage you can against their war resources. . . ." Since Atlanta was a vital supply, manufacturing, and communications center, Sherman advanced toward that point pushing Johnston back.
Sherman's advance started 7 May. Since Johnston's position at Dalton was too strong to attack, Sherman sent McPherson, preceded by Kilpatrick's cavalry division, to turn it from the west while Thomas advanced frontally along a railroad. Schofield threatened the Confederate right. This resulted in the minor skirmishes around Rocky Face Ridge, 5-9 May '64. Johnston withdrew without a major engagement.
Johnston took up a strong defensive position. The actions around Resaca, 13-16 May, were followed by another Johnston withdrawal when Sherman threatened another envelopment. Sherman now advanced on a broad front, since the country was more open. Garrard's Federal cavalry, supported by Davis's division, captured Rome, Ga., an important manufacturing and supply point. Johnston planned to take advantage of his own concentrated position around Cassville and Sherman's separated corps to strike a counterattack. While Hardee and Wheeler's cavalry checked the advance of McPherson and Thomas from the west and north, Hood on the right (east) was to attack Schofield as the latter moved with his corps to attack Polk in the Confederate center. Hood, however, was maneuvered out of position by the advance of McCook's cavalry on his own right; instead of preparing to attack west, he faced east to meet what he thought to be a threat to his own right. The delay caused by this error spoiled Johnston's plan, and the Confederates withdrew again to a strong defensive position south of Cassville.
On 19 May Thomas closed in from the west, and Schofield from the north. The forces skirmished until dark. Although Johnston had intended to defend here, Hood and Polk convinced him that their part of the line was too vulnerable. Johnston, therefore, retreated again during the night of 19-20 May to Allatoona Pass.
Sherman found this new position too strong to assault. After giving his army three days' rest, he undertook another turning movement. McPherson's Army of the Tenn. moved on a wide envelopment through Van Wert and approached Dallas from due west. Schofield on the left and Thomas in the center approached from the north. This brought on the action at New Hope Church, 25-27 May. Sherman then moved east again and forced Johnston to abandon his position to take up another one to protect the railroad. This led to the battle of Kenesaw Mountain, 27 June. Here Sherman deviated from his former strategy of turning, rather than assaulting, Confederate defenses; the result was a bloody repulse. Polk was killed 14 June at Pine Mountain.
Johnston's next stand was on the Chattahoochee River, 4-9 July. Sherman again turned his position and Johnston withdrew to Peach Tree Creek. Hood, who was known for his aggressiveness, relieved Johnston on the evening of the 17th.
Sherman closed in on Atlanta from the north and east. McPherson executed the wide envelopment through Decatur. Thomas crossed Peach Tree Creek from the north. Schofield was between these wings. In the battle of Peach Tree Creek, 20 July, Hood suffered heavy casualties and failed to defeat Thomas's army. When Hood withdrew into the defenses of Atlanta, Sherman erroneously concluded that he was abandoning the city. As McPherson issued orders to move in pursuit to the south and east of Atlanta, Hood sent Wheeler and Hardee on a 15-mile night march against McPherson's exposed south flank. This action, in which McPherson was killed, is known as the battle of Atlanta, 22 July. The Confederates, however, were finally checked with a loss of about 8,500 as compared with a Union loss of 3,700.
July ended with Hood holding Atlanta with 37,000 infantry reinforced by 5,000 Georgia State Militia. Sherman had 85,000 infantry.
Sherman then prepared to deploy his infantry. The night of 25 Aug. he started regrouping his forces to turn Hood's west flank. On 27 Aug. his forces were on line along the Sandtown Road with Howard, Thomas, and Schofield from right to left. The next day Howard and Thomas reached the Montgomery and Atlanta R.R. at Fairburn and Redoak Station. By midnight of 31 Aug. Schofield had cut the railroad at Rough and Ready; Thomas had cut it about halfway between that place and Jonesboro. Howard had closed up to the latter place from the west.
The night of 30 Aug. Hood, knowing of Howard's location but not that of the other two commanders, had sent the corps of Hardee and S. D. Lee to defend Jonesboro. The next day they made an unsuccessful attack. S. D. Lee was then ordered back toward Atlanta. Sherman then failed to destroy Hardee's isolated force. These actions are known as the battle of Jonesboro, GA., 31 Aug.-l Sept. '64.
Hood evacuated Atlanta at 5 p.m. 1 Sept., and the XX Corps took possession the next morning. Sherman pursued Hood to Lovejoy but found him in a position that was too strong to be assaulted. Union forces returned to Atlanta 4-8 Sept. Unable to advance farther, but determined to hold his gains, Sherman evacuated the Southern civilians from the city and converted it into an armed camp that could be held with the smallest possible force. In Sept. Hood moved north to attack Sherman's 140mile line of communications to Chattanooga, with the hope that this would force him to abandon Atlanta. This operation is known as the Franklin And Nashville Campaign. After stopping Hood's threat to his line of communications and then leaving Thomas to take care of Hood's subsequent invasion of Tennessee, Sherman cut loose from his base in Atlanta and started his famed march to the sea.