I keep getting visions of a Roman take on an old Poul Anderson story 'The High Crusade'.
Ignoring the apparently awful film the basic premise of the original book was a small group of Norman knights and their English serfs coming into contact with a rampaging Alien race getting lost in space and then finding out precisely how much damage nuclear bombs fired from trebuchets could do.
Just picture the Roman reaction to the Kalkrisse disaster, amongst others, if they had nuclear capability - most of northern Europe and the near East would probably still be glowing in the dark