The student of the siege of Petersburg does not need to know as much about 1864's Atlanta Campaign as about that year's Shenandoah Campaign; the latter was far more intimately related to the siege. As far as the Atlanta Campaign is concerned, it is necessary to know that as Grant's second offensive collapsed near June's end, the general-in-chief determined to restricct Federal efforts to Georgia and Virginia and informed Sherman that he needed no longer worry about the Army of Tennessee detaching forces to Lee. By August, with Grant's army stalled in front of Richmond and Sherman's progressing toward Atlanta's last railroad, the general-in-chief worried lest he be ordered to raise the siege of Petersburg in order to deal with matters elsewhere. OR 40, 2:193-194. Grant thought that lifting the siege would permit the foe to concentrate against and defeat Sherman. Ibid. As long as the general-in-chief kept the pressure on Lee in Virginia, any Confederate reinforcement of the Army of Tennessee would have to come from elsewhere.
Still, the student of the siege of Petersburg can contribute more than that to the understanding of 1864's Atlanta Campaign. The contribution will be to the big picture, rather than to the minute details. The first issue on which the student of the Petersburg siege can shed light is on the choice of a commander of the Army of Tennessee before beginning of the campaign of 1864.
Currently, the two major books on the Atlanta Campaign are Albert Castel's Decision in the West: The Atlanta Campaign of 1864 and Richard M. McMurry's Atlanta 1864: Last Chance for the Confederacy.
Castel says that after Gen. Braxton Bragg resigned and senior corps commander Lt. Gen. William J. Hardee declined command, Davis was left with only three choices for a commander of the Army of Tennessee: Gen. Robert E. Lee, Gen. Joseph E. Johnston (upper left, courtesy of National Archives), and Gen. P. G. T. Beauregard (right, courtesy of National Archives). No one could replace Lee as commander of the Army of Northern Virginia, Castel explains that appointment of Beauregard would admit that his relief as commander of the Army of Tennessee in 1862 had been a mistake, and that left Johnston. Davis detested both Beauregard and Johnston, and they detested Davis. Castel, Decision in the West, 28-29. Castel's explanation of Johnston's appointment is probably right.
McMurry considers insurmountable the problems Davis would have faced selecting a commander of a subordinate rank rather than a full general. Like Castel, McMurry believes the practical choice boiled down to Beauregard or Johnston, McMurry attempts to justify Davis's choice of Johnston because of Johnston's seniority, his extensive experience in command of a large army, his personal bravery, his modest administrative ability, and his popularity. McMurry, Atlanta 1864, 6-9. Johnston was indeed senior to Beauregard, but the latter also had commanded a large army (after Gen. Albert Sidney Johnston's death), was personally brave, had administrative ability, and was popular.
Siege of Jackson, Mississippi, July 9-17, 1863
The Official Atlas of the Civil War, Plate XLIV, 2
Furthermore, since Johnston's initial victory at First Manassas/First Bull Run, where Beauregard assisted him, Johnston had succeeded neither on offense or on defense. Beauregard and Johnston had both launched unsuccessful attacks, Beauregard at Shiloh (assisting Albert Sidney Johnston) and Joe Johnston at Fair Oaks/Seven Pines. Johnston had failed to defend Jackson and Vicksburg, Mississippi, and Beauregard had failed to defend Corinth, Mississippi, but Beauregard had successfully defended Charleston, South Carolina. Maybe President Davis thought that the results at Charleston would have been the same if Joe Johnston and Beauregard had changed places, but the successful defense of Charleston against a powerful Federal fleet and substantial land forces might have at least suggested what the campaign of 1864 would confirm: Beauregard was a better general than Johnston, much better.
In May 1864, while Joe Johnston was revealing his incompetence by failing to defend Snake Creek Gap against Sherman, Beauregard was successfully attacking Butler at Second Drewry's Bluff (May 16) and driving him back into Bermuda Hundred. In June 1864, while Johnston continued to retreat before Sherman, Beauregard brilliantly defended Petersburg against Grant's first thrust toward the Cockade City (June 15-18). Beauregard's record in May and June 1864 was not perfect--his plan for a counteroffensive on June 24 was faulty--but his record was far better than Joe Johnston's.
Does all this mean that Davis made the wrong decision choosing Johnston instead of Beauregard to command the Army of Tennessee at the beginning of the 1864 campaign?
Only if a 1-1 defense record since First Manassas/First Bull Run outweighed a 0-2 defense record, and then, because of Beauregard's previous dismissal from command of the Army of Tennessee, any error was hardly glaring.
More interestingly, even if selection of Beauregard had benefitted the Army of Tennessee, any such benefit would likely have come at the expense of Petersburg and Richmond.
With Beauregard in charge of the Army of Tennessee, Johnston would have had to take Beauregard's place in the east. Bragg could not trade places with Johnston to take Beauregard's place in the east because Johnston serving as Davis's personal advisor is unthinkable; the two men loathed one another. General Samuel Cooper, the ranking Confederate general, was strictly an administrator.
Does anyone imagine Johnston successfully attacking Butler and driving him away from Richmond and back into Bermuda Hundred? Does anyone imagine Johnston successfully defending Petersburg against Grant? Selection of Beauregard to command the Army of Tennessee at the beginning of the 1864 campaign might well have cost the Confederacy Richmond as early as May.
Davis needed three good generals for the campaign of 1864, but he had only two at that rank.
