"...for such a forgotten battle, especially in the long shadows of Nashville before it and Atlanta and the March to the Sea after, was nonetheless among the most harrowing of the war. Pershing described the conditions his men were exposed to at Chattanooga as "medieval," and the campaign earned the moniker "the Red Snow" on both sides of the fighting. So when the breakthrough finally came in early February and his men were raising Old Faithful over hills on the other side of the Tennessee River they had stared grimly at for nearly three months as shells landed around them and they were as likely to freeze or starve to death as to die of their wounds, Pershing felt nothing other than relief and a determination to push on once his forces had suitably regrouped. They had fended off multiple counterattacks and even come back after having to retreat ten miles inland from their initial lines after a particularly violent and temporarily successful Confederate offensive, but now Chattanooga was theirs - the Tennessee Campaign, after nearly two horrifying years, was finally at an end. [1]
Strategically, Chattanooga was an important victory because it placed American forces in control of the entire Tennessee Valley but more crucially set them immediately on the edge of Georgia, thus touching that state for the first time in the war other than raids against Savannah from the sea. The previous capture of Knoxville and the fighting in Middle Tennessee had already significantly diminished the city's importance as a rail junction, however, and as they had previously in Nashville and much of Kentucky, Confederate planners had been clever about evacuating the vast majority of the city's light industries southwards. Now Georgia stood ahead, and as Pershing wrote to Stimson and Bliss on February 19th as he stood staring out over the snowy Appalachian foothills, "we shall deny them anyplace further to evacuate."
Pershing's men were utterly spent, however, and needed badly to regroup, and partisan attack by the Irregular Divisions had badly strained his supply lines at the height of winter, and so he identified early April as the target for his push into Georgia, with the city of Rome upon the confluence of the important Coosa his first objective. In drafting the plans for the Georgia Offensive with his two most trusted subordinates in Harbord and Menoher, Pershing determined that a massive drive to Atlanta would be the first stage of the campaign, and once the city was in his hands, his army would spread out into several columns across Georgia, with different destinations - Augusta for the left flank, Savannah for the center, and Columbus and finally Valdosta for the right flank. From there, these newly divided armies could easily punch into central and coastal South Carolina, with the factories of the Upcountry and Charleston in their crosshairs, while the westernmost formation would push towards Tallahassee and Jacksonville, thus finally cutting the Confederacy entirely in two. As such, Pershing viewed his campaign as considerably more critical than Lenihan's increasingly delayed push into Virginia, as it was in Georgia and, thereafter, South Carolina where the war would be won.
To that end, his near two-month pause to regroup and resupply was not just done to bring in fresh divisions of men for the final push but also to make sure that he had sufficient air cover, especially newer "diver-bombers" that had been developed by the Curtiss Aeroplane Company of upstate New York, to utterly harry the enemy from the sky as well as a full armored "cavalry division" of landships to push through enemy defenses. Harbord especially was skeptical that much could be achieved in the coming offensive without all these supplies, as more short-term attacks over the preceding year had always been limited by the American supply situation being superior, but not overwhelming. Confident that the Confederacy had no proper deterrent to these kinds of weapons, Harbord advocated doing the campaign "correctly, the first time, rather than correctly after learning from several mistakes that cost us thousands in human treasure." Pershing concurred, and as always, Bliss smoothed over any frustrations back in Philadelphia that he wasn't moving quickly enough.
Pershing would be glad he had taken the time to ponder his offensive, in the end. His thrusts towards Rome and Gainesville, meant to capture small factory towns on their own merits but also give him pincer positions to the northwest and northeast of Atlanta, were badly stymied by spring floods on the Coosa and Chattahoochee Rivers. Reconnaissance behind enemy lines also revealed that, after Chattanooga, the entire command structure of the Confederate defense of Georgia had been revamped, with all divisions stretching from the South Carolina state line on the Savannah River to Birmingham, Alabama consolidated under the command of General Mason Patrick, the man who had successfully led the initial invasion of Maryland and Pennsylvania but been sent south for failing to prevent the collapse at the Susquehanna. Pershing had been concerned about facing Patrick head-to-head as it was simply in the environs of Atlanta, but especially now that he once again enjoyed a theater-level command. It was generally thought within the US War Department that Patrick was one of the most capable and clear-eyed Confederate senior generals and the successes in the Eastern Theater were, in large part, a byproduct of no longer having to face him directly in the field. Patrick had also become extremely well-versed in logistics having had a command in Atlanta, the beating heart of the Confederate transport network, for close to two years and understood his local geography and its defenses backwards and forwards. In other words, despite the end of the war potentially being in sight, Pershing understood perhaps better than anyone how difficult his objective would be, clear as it was on paper.
The Atlanta Campaign had begun..."
- Pershing
[1] In the spirit of me finding writing the blow-by-blows boring, just know that there was a bloody, terrible campaign around Chattanooga roughly modeled on Sherman and George Thomas's push for the city of OTL in the ACW, with corresponding Confederate counterattacks.