How will it be chosen now if i follow his call? Do I just do what my Captain/sargent says? Do I get any option to choose if I want to participate? What if my Colleagues know that I voted for him? I know it's a very generalized question and it probably differs from case to case, I'd still love to get an insight to what's happening to a standard soldier in these situations.
It's not focused entirely on the lower echelons on the military, but this older answer of mine on how the military chose sides during the attempted coup in Spain in July 1936 might shed some light on the dynamics involved.