After WW I, Fort Myer was where the famed 3d Cavalry - Brave Rifles - were stationed until they relinquished their horses in 1942 and headed to Georgia to become mechanized. When this film was made, COL George S Patton Jr. was commander of Fort Myer and the 3d Cavalry.
Thanks to my extensive network, a video clip which was made in 1934 surfaced of these troopers exercising their mounts with sabers drawn on the drill field on Fort Myer. This joins the other three items that I've found that were filmed on Post:
the 1909 flight of the Wright Flyer with Orville Wright & LT Frank Lahm
the 1934 Movie "Keep 'Em Rolling" that introduced the Caisson Song
the 1957 segment of The Big Picture with TUSAB* & TOG** on Summerall Field
For your viewing pleasure, I present below to you the Brave Rifles on Fort Myer performing one of the last saber drills (one can see the "Three Sisters" in the background as the troopers head down the drill field)
You can learn more about the "Brave Rifles" and the historic Fort Myer where they were posted in the book "Images of America - Fort Myer"
*TUSAB = The US Army Band
**TOG = The Old Guard - 3d INFANTRY Regiment