Odds of Hanging On
The bright side (for Military Battlefield Surgeons at least) is that there continues to be armed conflict happening all over the world. Which means there will be a continued demand for your services. In other words, being sewn back up after "absorbing" a few chunks of metal is not some fad that will go out of style in a few years. People like to be whole, so you're good there.
The other thing is that this is the military. They don't look kindly on their doctors (or anyone for that matter) quitting. It's called going AWOL. This means you are kind of required to hang on.