IMO, in the military they are reshaping them to fit into a unit. So, like a bone that has been incorrectly set, their spirit is broken, realigned, and then allowed to grow whole again.
But for martial arts, I think it should be more like muscle training: we want to push their spirit as far as it can be without injury so it grows back stronger. If we tear that spirit, it must heal first before resuming training.
I would comment that, in my experience with the military, I did not hear much about breaking a soldiers spirit. I think a major factor is training someone to survive the initial shock of real life and death combat, and that involves building a set of skills that get the soldier through the initial tendency to freeze. Drawing parallels between martial "arts" and true martial training for war has limitations.