This is more to settle an argument between some me and a mutual friend, who for some reason doesn't understand that this would be a complete blowout. Admittedly, he's a huge Halo fanboy, and I doubt he's delved even a little into the Warhammer material I've provided him, but seeing as I'm almost an equally huge WH40k fan (I have played all the Halo games, including the RTS), I want to make sure I'm not being totally unreasonable here.
Do the Covenant, the alien menace of the Halo Franchise, even stand a chance against the arrayed forces of the God Emperor of Mankind?
I think it's at least an interesting question given how many parallels can be drawn between Halo and WH40k (I think you can even make an argument that the Adeptus Astartes more or less inspired the Spartans, as much as any other games space marines). I maintain however that in any armed conflicts, the filthy xenos worshiping their alien gods do not stand a chance against the Imperium's finest.
Sheer overwhelming logistical strength on the part of the humans. It's true that the ungainly Imperium stretches thousands of worlds and faces so many threats that it's combined might cannot ever be brought to bear against a single foe, but assuming the Covenant ever launched a major campaign against an Imperial sector, they'd be facing down forces in a scale we've never seen in the Halo universe (even the books).
Again though, I want some opinions from the Halo supporters our there in the Playground. What are the largest feats of military might we've ever seen the Covenant launch (Reach is the greatest battle I can think of) and can they even hold a candle to the deeds of a single Space Marine Chapter?