Doctors of the time did their best, but often as you say did more harm than good.
In our Civil War about two soldiers died from disease or wounds as opposed to being killed directly in combat. This was, however, much better than any previous war. If I remember rightly, the ratio was 7:1 for the Mexican War and higher than that for the Revolution.
The survival rate for wounded soldiers has gone up spectacularly, to the point where we drastically underestimate the violence of the Iraq and Afghanistan wars because they have caused comparatively few American deaths. This is more a function of the efficiency of the medical care they receive than it is of lowered violence.
The same is probably true of the vaunted decline in the US murder rate. It is largely due to fewer people dying because of better trauma care, not to a reduction in violence. IOW, people are still getting shot at a high rate, but more of them are surviving the experience.