Inglot, Jacek. Quietus
Divergence: 363 CE
What if: Emperor Julian the Apostate decided not to fight Persia, and Rome didn't fall. All Christians are murdered or escaped to Japan.
Summary: In the 8th century, Rome has developed steamships and placed factories as far east as (our) Indochina. Now, Christianized Japan declares war on pagan Rome.
Published: Zysk i s-ka 1997 (8371502877).
— Expanded from "Quietus i chrzescijanie" [or "Quietus and the Christians"], in Wizje Alternatywne: Antologia opowiadan SF (ed. Wojciech Sedenko), ARAX 1990 (8385211055).
Original in: Polish.