If you're not familiar with the Warhammer 40,000 universe, take your standard fantasy world and project it forward 400 millennia so the orks and elves are riding around in spaceships and the Knights Templar use chainsaw swords. The game's story (a direct sequel to the original game) is some piffle about the Blood Ravens' attempt to retake the recruiting world of Calderis before it's destroyed by Orks, Eldar and a ravening swarm of Tyranid. Ultimately though, it serves the same purpose as any bit of fluff in the Warhammer 40,000 universe -- giving a thin skin of order and sense to what is basically a Frank Frazetta painting with black leather chains and laser guns.

The single-player campaign is where the player first gets an indication of the changes.  As the player progresses through a branching mission structure, they'll eventually take control of six different Space Marine squads that each come with unique abilities. Cyrus for example, is a Scout Marine that excels at stealth, infiltration, and long-range assassination. Avitus, on the other hand, is the group's heavy weapons guy, who can be tasked to use heavy bolters to suppress enemy fighters, use heavy rockets to take out vehicles, or become a sort of mobile artillery crew.The game completely eschews the traditional RTS build-farm-construct gameplay paradigm in favor of a squad-level tactical game that's actually pretty far down the road toward being an action/RPG.