LOL!A military origin for dressage seems likely. Getting everybody all neatly arrayed and then having control in close combat.
Yes, actually, dressage does have its beginnings in the military. It is the high school (haute ecole) for horses. It is intended to train them not only physically so that they can carry a person with greater balance and comfort (for both you and the horse), but to school the horse's mind so that he is attentive and responsive to your requests.
Dressage is based on old perverts wanting to see young women in pants so tight it's embarrassing. And then there's the camel toe. Sorry, was that out loud again?
Then why are the top dressage riders all men? And STRAIGHT men, for the most part.
Sorry, when I watch dressage I'm not looking for men. Though the men can be straight, it doesn't matter to the pervs that are staring at their packages.