Pursuant to your screenname and relevant to that video, something I remembered reading decades ago that illustrates how horses were trained as much as humans to the point of drills being second nature.
Perhaps managing to patch some up to the point that they could be sold at auction like the 20 bad cases that Sir Astley Cooper bought (purportedly mounts of the Garde [Scots Guard?]Cavalry). Cooper had been moved by the plight of the animals, and being a noted surgeon and anatomist who had recently taken a keen interest in the anatomy of animals determined to buy them, with a view to rehabilitating them. Cooper was a prominent man, a Copley Medal winner, Fellow of the Royal Society and professor of comparative anatomy at the Royal College of Surgeons, with an annual salary of 21,000 pounds in 1813.
He had the horses shipped to England under the care of six grooms and had them transported to his park in the country, were he spent months removing musket balls, grapeshot and stitching the sabre cuts from their bodies and limbs. Amazingly he was successful and he was soon able to turn them loose in the park, were they exhibited an unusual behavioural trait of their distinguished service.
One morning Cooper observed the horses gather together in a line and advance to a charge across the field, halt, retreat and then gallop about excitedly. Their evident pleasure at their new lot in life delighted Cooper, who was treated to this display most mornings, as were most visitors who came by. Kelly remembered a horse that showed a similar hang up from its violent past. “An officers horse, which survived the battle of Waterloo, still retains a lively recollection of the wounds received on this occasion; the clamour and bustle of the engagement seem to have perpetuated in his ears:- when anyone approaches him in the stable, he puts himself on alert for a charge, and starts, as if to avoid a sabre cut”.
Abstracts of a Battle. - Adventures In Historyland
This is a fairly large mash up of four subjects dealing with peripheries and little known areas of the Battle of Waterloo. Here I’ll tell you about some of the women of Waterloo, of how news reached Britain, of the suffering and treatment of the horses who fought at the battle and discuss the …...adventuresinhistoryland.com
I think we should all be careful of templating our 21st century bias (and ignorances, considering how horses now are far more of a curiosity than a reality these days).
Full disclosure - learned to ride practically in the Kentucky hills north of Fort Knox a few decades ago while a young LT, taught by a Cavalry SSG spending his last year assigned to Range Control.
So this video floated to the top of my Youtube cue and illustrates perfectly what trained (but riderless) horses are capable of doing.