On November 12, 1864 the destruction of sections of Atlanta began under Sherman’s chief of engineers, Captain Orlando Metcalfe Poe.
Sherman had expelled the civilian population from Atlanta in September. Go here to read about it.
Forced relocation of civilians and the burning of towns and cities is not uncommon in war. George Washington was given the nickname “town destroyer” by the Iroqois after Sullivan’s expedition in 1779 where, under Washington’s orders, numerous Indian towns and villages were destroyed in retaliation for raids against the Americans. Sherman burned Atlanta because he did not want it turned into a Confederate base in his rear as his Army marched to the Sea. A perfectly legitimate, although unpleasant, aspect of war. Of course similar tactics were used by the Confederates in areas they considered disloyal, such as East Tennessee which was heavily Unionist in sympathy. Sherman did not burn churches or hospitals, and ordered that no dwellings be burned. The burning he ordered was to be limited to the business and industrial sections and any Confederate property that Hood had not burned when he retreated from the city. However many civilian dwellings were burned against Sherman’s orders, mostly by civilian looters who had stayed behind to rob vacant house. About 37% of the city was destroyed. The civilian population returned within three weeks later and were well on their way to rebuilding the portions of the city destroyed before the end of the war. The burning of Atlanta was rough business, but it was not a major war atrocity.
Here is Sherman’s brief mention of the destruction in his memoirs:
I reached Atlanta during the afternoon of the 14th, and found that all preparations had been made-Colonel Beckwith, chief commissary, reporting one million two hundred thousand rations in possession of the troops, which was about twenty days’ supply, and he had on hand a good supply of beef-cattle to be driven along on the hoof. Of forage, the supply was limited, being of oats and corn enough for five days, but I knew that within that time we would reach a country well stocked with corn, which had been gathered and stored in cribs, seemingly for our use, by Governor Brown’s militia.
Colonel Poe, United States Engineers, of my staff, had been busy in his special task of destruction. He had a large force at work, had leveled the great depot, round house, and the machine-shops of the Georgia Railroad, and had applied fire to the wreck. One of these machine-shops had been used by the rebels as an arsenal, and in it were stored piles of shot and shell, some of which proved to be loaded, and that night was made hideous by the bursting of shells, whose fragments came uncomfortably, near Judge Lyon’s house, in which I was quartered. The fire also reached the block of stores near the depot, and the heart of the city was in flames all night, but the fire did not reach the parts of Atlanta where the court-house was, or the great mass of dwelling houses.