Free in the Baen Free Library:
https://www.baen.com/training-for-war.html
Below, From the Promotional 'blurb' on the Baen site:
"An essay and manual on training for war by retired Army lieutenant colonel Tom Kratman, creator of the popular Carrera military science fiction series, including novels A Desert Called Peace, Carnifex, Come and Take Them, and The Rods and the Axe. Kratman’s contention: an army is for winning wars. And to win wars, you have to train men (and some women) to be warriors, not police or social workers. Herein Kratman gives guidance and a practical plan of action to officers tasked with training troops—advice than might be equally applied to other crucial training situations, as well."