How long does it take the army to train a field medic? (Serious question, I don't know if there's some extended training involved, I just assume it's far less than, say, a nursing degree.)

I think that training people to handle 90% of the issues you see in Covid-related illnesses could be done relatively quickly, if we wanted to do that. The ICU bed shortage really refers to a ICU-staff shortage, and anything we could do to relieve that burden would be a good thing.