My understanding, as limited as it is, is that the German model requires mandatory national service. That doesn't necessarily mean the military. It could be working in a seniors' residence. It could be driving an ambulance, just to free up a paramedic to actually work on a patient—those kinds of things.
Yes, there are definitely people who volunteer for the Technisches Hilfswerk, the THW, which is the model we're discussing. Those people then continue to volunteer, many of them for the rest of their lives, doing different sorts of disaster responses.