The substantial re-education of the Polish Armed Forces has necessitated replenishment of the number of reserve personnel. To this end, new forms of short military training for volunteers have been introduced, in line with the objective that within the next few years the number of soldiers and civilian employees of the military will initially exceed 200,000, and later 300,000. The aim of this article is to analyse the possibilities of increasing Poland’s defence capacity through in-service training for teachers of military preparation units. The research included analysis of the literature on the subject of military education classes in Poland, as well as the study of regulatory documents in the area under consideration. Theoretical research methods such as analysis, synthesis and inference were also applied. The study presented here includes an account of the origins of the military preparation units and a description of the features of the in-service training for teachers of those units, conducted at the War Studies University.