A military training approach was first introduced in 1888 at the Elmira Reformatory in Elmira, New York (Anderson et al., 1999).  This new training approach was implemented to invoke discipline and keep the inmates active, rather simply allow them to suffer boredom and inactivity.  This lasted until 1920 when the horrors of World War One meant this form of training fell out of favour (Smith, 1988).

References:

Anderson, J.F., Dyson, L. & Burns, J.C. (1999) Boot Camps: An Intermediate Sanction. Lanham, Maryland: University Press of America.

Smith, B.A. (1988) Military Training at New York’s Elmira Reformatory 1888-1920. Federal Probation. 52(1), pp.33-40.