Roma DCX was one of many alternate timelines where the Roman Empire never fell. There, Emperor Nero embraced Christianity and made it the state religion. Later, a schism occurred between the western empire centered in Rome and the eastern empire centered in Constantinople, resulting in two millennia of crusades and counter-crusades and an arms race that pushed military strategy to its extreme. Each empire was led by a Pope-Emperor.
This Roma was the first to be invaded by the Nazis. (PROSE: Warlords of Utopia)