The campaign began with Johnston holding strong defensive positions at Buzzard's Roost Gap and Rocky Face Ridge, which he hoped Sherman would assault.

He was compelled to abandon Dalton when the Union Army of the Tennessee under James B. McPherson seized the unguarded Snake Creek Gap on May 8, threatening Resaca from the west.

Johnston retreated to Resaca where he was joined by reinforcements gathering there; he was pursued by Sherman, most of whose forces followed McPherson through Snake Creek Gap, while others came south down the Western and Atlantic Railroad.

On May 14, Sherman gained a foothold west of Resaca but an attack on Confederate defenses to the north and northwest was repulsed, as was an assault by Johnston on the Union left flank later the same day.

On May 15, Sherman's attack to the north and a Confederate counterattack were both stopped, but other Union forces seized a bridgehead on the south bank of the Oostanaula River.

On April 30, Sherman commanded the Military Division of the Mississippi and gathered a field army numbering 110,000 soldiers of which 99,000 were available for "offensive purposes".

[2] The 25,000 non-combatants accompanying the army included railroad employees and repair crews, teamsters, medical staff, and Black camp servants.

[19] When Jefferson Davis awoke to the danger Sherman posed to Georgia, he authorized Polk to send Loring's division from Mississippi and an infantry brigade from Mobile.

[25] Cleburne later wrote that Johnston's chief of staff William W. Mackall told him that the gap was undefended because of "a flagrant disobedience to orders", but did not name the guilty party.

McPherson, worried that he was walking into a trap, recalled both of Dodge's divisions and marched his command back to Snake Creek Gap after losing 6 killed, 30 wounded, and 16 captured.

When reports of Union forces at Snake Creek Gap reached Johnston, the Confederate commander sent the divisions of Cleburne and Walker to Tilton, north of Resaca.

Later that day, Thomas also arrived and informed Sherman that Johnston's wagon train was sighted moving south toward Resaca, indicating that the Confederates were probably retreating.

By 4:30 pm, Logan's troops drove the Confederates from Bald Hill and confronted a heavily defended line of entrenchments outside Resaca.

Stoneman's and McCook's cavalry and Howard's IV Corps pushed south from Dalton, slowed by Wheeler's effective delaying tactics.

[36] Sherman thought that Johnston intended to retreat from Resaca, a belief strengthened by seeing the Confederate wagon train crossing to the south bank of the Oostanaula.

The Union soldiers blundered through heavy underbrush and suddenly confronted Confederate entrenchments on the east side of Camp Creek.

Henry M. Judah's XXIII Corps division recklessly charged, ran into intense rifle and cannon fire, and was bloodily repulsed.

On Judah's left, Cox's XXIII Corps division encountered an advanced line of rifle pits and seized them after a bitter struggle.

[39] At 4 pm, Johnston noticed that David S. Stanley's division of Howard's corps had its left flank exposed and ordered Hood to attack it.

Stanley called for help, formed his division into a long thin line, and posted Peter Simonson's 5th Indiana Battery on the extreme left flank.

Stevenson's soldiers overwhelmed Stanley's two left brigades but when they tried to overrun the 5th Indiana Battery, they were driven back by deadly fire from its six M1857 12-pounder Napoleons and 3-inch Ordnance rifles.

Stevenson's division tried a second attack and was repulsed by some of Stanley's rallied Union infantry and close-range blasts of double canister shot from the cannons.

[40] During the afternoon, Peter Joseph Osterhaus detected weakness in the Confederate skirmish line and pushed the 12th Missouri Infantry forward.

At 7:30 pm, Cantey's division and Alfred Jefferson Vaughan Jr.'s brigade tried three times to retake the hill, but failed in the face of cannon projectiles from Louis Voelker's Battery F, 2nd Missouri and rifle fire.

However, William Thomas Ward's brigade, led by Benjamin Harrison's 70th Indiana Infantry Regiment, found itself in front of Max Van Den Corput's Georgia Cherokee Battery and charged, overrunning the guns.

[50] After Johnston heard that the Federals were no longer a threat at Lay's Ferry, he ordered Hood to attack the Union left flank again.

Hovey's XXIII Corps division, formed of recruits, was supposed to support Williams, but instead its soldiers hugged the ground and refused to go forward.

[12][58] Sherman forced Johnston to abandon two "tactically strong defensive positions", though the Confederate army was able to escape intact both times.

[60] Sherman hoped to catch up with and crush Johnston's retreating army between the Oostanaula and the Etowah Rivers, a distance of 30 to 40 mi (48 to 64 km).

[61] Sherman sent Garrard's cavalry, followed by Jefferson C. Davis' XIV Corps division, down the west bank of the Oostanaula toward Rome.