(I am going by faith that this is about Carlson's Raiders; the predecessors of Marine Force Recon. I can't get the YouTube video to load.)
I have the movie with Randolph Scott and Robert Mitchum. The selection process was unworldly.
In ways, it was like Delta selection, both physically and mentally: and it messed with their heads.
One of the culling methods used was a 40 mile forced march, at a 5 MPH pace, with a heavy pack.
That friends is SEAL Team 6/Delta Force territory.
In WWII, they were buried where they fell, and no attempt was made to send them home to the US.