In 1862, Barton finally gained permission from Quartermaster Daniel Rucker to work on the front lines. She worked to distribute stores, clean field hospitals, apply dressings, and serve food to wounded soldiers in close proximity to several battles.

In 1864 she was appointed by Union General Benjamin Butler a the "lady in charge" of the hospitals at the front of the Army of the James.

Among her more harrowing experiences was an incident in which a bullet tore through the sleeve of her dress without striking her and killed a man she was tending. She was known as the " Angel of the Battlefield."

" A ball had passed between my body and the right arm which supported him, cutting through the sleeve and passing through his chest from shoulder to shoulder. There was no more to be done for him and I left him to his rest. I have never mended that hole in my sleeve. I wonder if a soldier ever does mend a bullet hole in his coat"