Sherman's plan was simple.  George Thomas and his Army of the Cumberland would cross the Chattahoochee River and hold the Confederate Army of Tennessee in place while McPherson and Schofield moved east to sever the rail connection to Savannah.  Executing this strategy successfully would increase the amount of time for Confederate reinforcements to arrive from Richmond, lengthen Johnston's lines of communication, and reduce the Confederate Army's access to grain and meat from Georgia's agricultural belt between Atlanta and Savannah.

Unbeknownst to Sherman, General Johnston did not plan to defend the Chattahoochee as Sherman anticipated.  Instead, Johnston planned to wait until Sherman crossed Peachtree Creek, then attack while the army was split in two.  Unfortunately for the Rebels, Johnston did not have the opportunity to counter Sherman's strategic moves.

On July 17, 1864, Confederate General Johnston received a telegram from Confederate President Jefferson Davis replacing the more cautious commander with a young Kentuckian, General John Bell Hood. Davis was disgusted with Johnston’s failures in the face of Sherman’s advances and did not believe that Johnston was aggressive enough to save the important Southern City of Atlanta. Hood had an uncomplicated aggressive temperament and "when they gave him Joe Johnston's army he assumed that he was expected to go out and fight." 

Regarding the change to Hood (pictured right), the Whig, a Richmond newspaper said, "The army and the people all have confidence in his ability and his inclination to fight, and will look to him to drive back Sherman and save Atlanta."

Sherman also welcomed the change in commanders, saying he "inferred that the change of commanders meant fight. This was just what we wanted . . . to fight in open ground, on anything like equal terms, instead of being forced to run up against prepared entrenchments."

After being repulsed by Rebels during an attempt to cross Peachtree Creek near Howell's Mill late in the day on July 19th, Union troops crossed further east and gained high ground south of the rain-swollen river. From this advantage, they took the crossing at Howell's Mill. A third crossing was built just east of these.

Concentrating to a line about a mile wide, the Union Army of the Cumberland crossed Peachtree Creek.  These troops were led by General George Thomas whose nickname, "the Rock of Chickamauga," was earned by skillful defensive fighting.  Immediately east of Thomas was the flank of McPherson's Army of the Tennessee and Schofield's Army of the Ohio forming a secondary line some eight miles in length.

Originally set to attack at 1:00 PM, the presence of these Union troops forced Hood to delay the initial Rebel assault until after 3:00 PM that afternoon while he strengthened his right flank.  This delay cost Hood the tactical advantage of having the Union Army split by the river as most had crossed by the time the battle started that afternoon.  Instead of attacking an enemy split by a physical barrier, elements of the Confederate Army were advancing on three divisions of the Union Army entrenched on high ground.