My understanding is that the defining feature of Sherman's Savannah Campaign was that he didn't actually try to occupy all the land between Atlanta and Savannah. He just walked his army from one end to the other, smashing any important infrastructure he found along the way, without bothering to maintain lines of supply or communication with the north until he met the navy at the end of the march. I.E. it was essentially a giant raid rather than an occupation outside of Savannah itself.
But whenever I see maps on the internet showing how territorial control changed over time in the Civil War (such as this popular one ), they always show a solid band of Union control between the two cities at the end of 1864. (and inevitably spawn lots of jokes about sawing the rebellion in half, or people praising the Union for cutting Confederate lines). My question is, is there any truth to the idea of Union forces being present in central Georgia blocking the movement of CSA forces after Sherman passed through, or is that just embellishment by cartographers eager to make the Confederacy's situation look really bad?
Context is needed to better understand the circumstances around Sherman's March to the Sea.
By the spring of 1864, after four years of war and half a million Americans dead, Union and Confederate forces were locked in apparent stalemate. The previous year's Gettysburg victory was a must-win for the Union and halted the South's northern advance, but Lee's army remained intact. President Lincoln was under tremendous pressure to end the Civil War. His political opponents were already advocating for peace with the Confederacy. Lincoln needed a big Union victory, a decisive one, to preserve the republic.
The Union Army commander, Ulysses S. Grant, and Sherman agreed that the destruction of the Confederacy's ability to wage war would hasten the end of the Civil War. They devised an operation that many historians would now describe as "scorched earth" policy or an early example of total war. Union forces would target and destroy the Confederates' economic and military infrastructure, marching deep into enemy territory, with the strategic aim of crippling the Confederacy's war machine. Railroads, cotton gins, mills, warehouses, bridges, telegraph lines, any infrastructure that might aid and support the Confederate cause would not be spared.
Territorial conquest was not the campaign's primary strategic intent -- it was to send a clear message to both the Confederate army in the field and its political leaders in Richmond: that continued fighting would achieve little and defeat was inevitable. Both Lincoln and Grant were wary about the campaign's risks and prospect for success, but they nevertheless trusted and respected the judgment of Sherman. Grant's instruction to Sherman was simple: "Go as you propose".
Sherman commanded an overwhelming Union force of more than 60,000, while the beleaguered Confederacy could only muster 1/5th of that size to oppose him.
Sherman's march began on Nov. 15th, 1864, departing the ruined city of Atlanta. It also had a second, more traditional objective: to apply rearward pressure on Robert E. Lee's Confederate army, now besieged to the north in Petersburg, Virginia, with the intent of giving Grant's Union army a chance to make a breakthrough or, at best, limit Confederate reinforcements from flowing to Virginia.
To achieve this with speed, Sherman would forego supply lines and allow his army to live off the land after using up 20 days of assigned rations. He used the 1860 census on livestock and crop production to determine the best foraging areas for the army.
One of his formal orders to troops was that civilian homes and farms would be left alone -- as long as the army was left unmolested on their journey. But if the Union army was harassed or assaulted during their progress south, they were given license to destroy local residences and buildings commensurate to the hostility shown to them.
Sherman knew that the army living off the land and burning homes would have a detrimental effect on civilian morale in the South and pressure them to seek a quick end to the conflict. His freeing of slaves from plantations, who were emancipated by Lincoln's 1863 Proclamation, was also traumatic to the South. In the eyes of the Confederacy, this potent reminder of the war's causes added insult to injury.
Confederate forces could only try to delay and distract a Union army of such size. They attempted to draw out Union troops away from their destructive path to the coast and the vital port of Savannah with feint attacks and raids, but Sherman's army (divided into two wings, confusing Confederate forces about Sherman's intents) largely declined to take the bait, all while he laid waste to the Confederacy's industrial and military arteries.
Sherman's army arrived in Savannah just before Christmas and soon defeated or drove off the smaller forces of Confederate troops defending the city outskirts. Achieving contact with the Union navy, Sherman was able to obtain the supplies and munitions he needed to invest the city proper. He gave his Confederate counterpart, General Hardee, a stark choice on Dec 17th: surrender the city, or face utter destruction. Hardee chose to evacuate his remaining troops and left the formal surrender to Savannah's mayor, who promised no resistance if Union troops pledged to leave its citizens and property unharmed. Sherman presented the capture of Savannah to Lincoln as a Christmas gift, along with 150 heavy guns, ammunition and 25,000 bales of cotton.
Sherman himself estimated that he had wrought $100M ($1.6B in today's dollars!) in destruction to Georgia and the Confederacy. In the wake of his march, much of the local populace was left homeless, starved, bitter and demoralized. The economic consequences in the South would linger into the early 20th century.