About 19 years ago I read a short story featuring, IIRC, a German WW2 officer, a Zulu warrior, and possibly a Roman centurion, who all wake to find they have been abducted and pitted in gladiatorial combat against alien beings.
I seem to recall the officer firing his Luger at some kind of armoured alien and the bullet ricocheting off its carapace, but otherwise I don't remember any specifics.
I believe the story may have been from the 60s or 70s.