Looks like a similar idea to the Desert Rock tests [1]. Though I don't think any of the Desert Rock soldiers galloped onto an atomic battlefield on horseback while wearing a gas mask and wielding a sword like one of the guys in your video did.
> Though I don't think any of the Desert Rock soldiers galloped onto an atomic battlefield on horseback while wearing a gas mask and wielding a sword like one of the guys in your video did.
I should note the horses are wearing gas masks too.
[1] https://www.youtube.com/watch?v=tXX-1MIMr2E