“The Obsolete Weapon” by L. Ron Hubbard
Publication date: May 1948
Original publication: Astounding Science Fiction
Genre: Science Fiction
Story description: An American soldier, transported from modern day Rome to the ancient Colosseum faces hungry lions, gladiators and elephants—and on his return, desertion charges.
Currently available as part of the Stories from the Golden Age series, in the title A Matter of Matter.