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Ok, this may be a silly question (or answered somewhere, I searched and couldn't find it if someone did answer it) but... What army is winning in the Warhammer 40,000 universe? Chaos is trapped (mostly) in the eye of terror, Imperium is being pounded by Chaos, Orks, and Tyranids, Tau are fighting Orks in a losing war, Orks are fighting everything, Tyranids are invading, Eldar are dying... What army is actually winning here? Is anyone or will everyone just lose ultimately?
I think the Tyranids will always be 'winning' unless someone comes up with a method of destroying the hive mind.
Also, the Tau are winning. They are expanding (what is it, 4th sphere of expansion now?) and the Imperium is ignoring them, so they should be fine till the Tyranids eat them. I don't know what your talking about with the Orks, the Tau style of combat is very suited to destroying Orks and I've yet to read about one piece of fluff describing a Tau loss to Orks.
Orks - more and more fighting is occuring, and fighting is all they care about
In the ork codex there's a section where it talks about one Warboss leading a fight against the Tau in their northern region of space... and just because Orks like to fight doesn't mean they're winning does it?
The whle idea is that it's basically a stalemate - no one side ever really gaining the upper hand over the others for long. This is for fluff balance and real world sales - if one side was pre-ordained to win you would see a shift in sales towards them - that's just the way people are. By having it like this we can stick to the "healthy balance" of Space Marines balancing against everything else.
So in summary - no one race is winning.
Chaos, simply because mankind aren't. This is chaotic victory, as the entire mortal realm is locked in an unending war. This is the chaos victory the Cabal talked about in Legion, why Abaddon never succeeds and why nine times out of ten, the Imperium wins the battles.
If Chaos ever truly won and converted and/or killed the entirety of mankind, there would be nothing left for chaos to do, but so long as there is killing in the name then Chaos can consider themselves winning without ever having a chance to win absolutely.
This is most active the four chaos gods have ever been and they don't want to change that. All other races; nids, necrons, tau etc are yet more irritants adding to the mess Chaos has made.
The 40k world is the very definition of chaos - a condition or place of great disorder or confusion.
As soon as one side wins, then the disorder and confusion will be replaced with sterility and calm - chaos don't want that and until an entity arises more powerful than the four chaos gods combined it won't ever happen.
I can't say I've seen it all but I live for the things that keep me hollow.
Necrons are winning of course....They can't lose.
Even if the 'Nids kill off every other biological organism in the galaxy, 'Crons will still be there to harvest the 'Nids
Mysterious Member of the ANZAC Clan
The glorious Imperium of the Emperor is winning.
Any other answer is heresy. (See above).
Im pretty sure the tyranids would win in a protracted war against the necrons simply because of numbers.