My concern about these ex-prisoners is what they do in the war zones.
Civilized armies do a lot of screening to keep out the mentally ill, the Psychopaths, and the inherently criminal, yet everyone knows that some slip through and that war uncovers new unknown ones, but to add 10s of thousands of the known ones to a combat zone must have unleashed a lot of hidden horrors.
My assumption is that most went into disciplinary type units where they were used to ferret out concealed enemy positions and deactivate landmines.