Its also why I believe most modern governments try REALLY hard not to go to war. Not because of the death and destruction but because they dont want a combat trained populace.
Also because shared adversity unites, the differences between people get really unimportant when they are trying to keep each other alive in combat.
The idea of a significant percentage of “us” coming back and being united and trained well enough to actually threaten the system scares the piss out of them.