I'm not saying it was aliens, but it was aliens.
From the release:
The last survivors of an alien race have escaped their dying star system and come to Earth. Their advanced technology allowed them to easily establish dominance over the Roman Empire. But with parts wearing out, no infrastructure, and small numbers maintaining power is another thing altogether...
Imperium Alieni puts you in the place of the aliens trying to hold on to power, or the humans who are no longer so much in awe of their alien overlords. Seven scenarios lay out a campaign that begins with some isolated guerilla actions and end in the aftermath of a total revolt. There's even a little surprise twist in the middle.
The .pdf contains:
Seven scenarios with set up, maps, and victory conditions
A campaign system to link the scenarios
Seven different possible locations for the scenario
Twenty pages of terrain templates to support the different locations
Full stats for our free QILS game, and guidlines for converting to other gaming systems