These clips are taken from old Army training films shot in California by the Signal Corps just as World War Two was about to change everything—especially the cavalry.
Because of the urgency of war, amazingly they tried to get raw recruits trained for the cavalry in a matter of weeks.
The army developed an entire system of training horses and riders and all the infrastructure and equipment needed, and then, within a few years it was all gone and the sport of Eventing moved into the civilian realm.
Thank you to David Roby, a New Hampshire equestrian and amateur historian for sharing part of his collection.