Answer: A. to isolate the city from the rest of the confederacy
The Battle of Atlanta was a Civil War battle, part of the Union's summer Atlanta Campaign. The battle occurred on July 22, with a decisive Union victory, but it would be another six weeks before Atlanta surrendered.
With the battle won, General Sherman established a siege of the city. On September 1st, he pulled out of the city, destroying supply depots as he left. The citizens surrendered the next day. Atlanta became Sherman's new headquarters, from which he launched his march to Savannah, known as the "March to the Sea," destroying everything in his path. Among the destruction, Atlanta's railroads suffered greatly, in an attempt to isolate the city from the rest of the Confederacy.
