Twelve thousand medical people volunteered their services to the Union army. They didn't learn asepsis very well. That had to wait for Lister, later that century. They used carbolic acid to wash the floors of the hospital and to clean up after the fact, but they didn't learn about washing before surgery. For some reason, they didn't make that connection.
Some people represent the surgeon as an uncaring butcher.
But the doctors were dedicated men. Yes, they did a lot of amputations. The muskets that soldiers were using could do terrible things. You had to make decisions very quickly. These men were really terrific people.