What, Belgium? No, it's Rome. Rome, you dummy. The eponymous nation was revealed by the game's official wiki, which will continue revealing factions at an undisclosed rate until the game launches next year.
"As a playable faction," the wiki reads, "Rome benefits economically from its excellence in metalwork, enjoys enhanced military development, and can exploit the masses in order to maintain public order." That's great and everything, but any true military strategist knows that the strength of a nation's soldiers depends entirely on the complexity and inventiveness of its plumbing technology.