I always assumed such usage was house ruled when I saw posts about it! Some points of clarification on terminology, if you would:
"Combat as War," similar to Gygaxian 'skilled play' the idea that player decisions and strategems and even (too put too fine a point on it) meta-gaming, should be able to swing the results of a challenge (especially a combat) to an extreme degree, possibly rendering the system itself (and certainly an encounter guidelines) moot.
My party had a grudge match set up with an ancient (elder wyrm? whatever it's been since they changed it from 1e's 'Ancient' - oldest age class) Mercury Dragon. Without getting into too much backstory....
...no, nevermind, here goes:
Back in mid-late Paragon, they were on an involved quest for a never-opened Pandora's-Box-like artifact. It led them through spelljammer space to remote crystal spheres, including one inhabited by Mercury Dragons (as in, how many Dragons could a world support if they and their Arkhosian-remnant-population Dragonborn servants were the only things living there more intelligent/powerful than tasty mammoths), and blockaded by a Neogi-led fleet (because the answer is /way too many to ever be allowed to leave the planet/). So the Dragons rule the world, eldest/most-cunning on top, and, in ancient days, 'The Great One,' most powerful of their race ever to exist, withdrew into his ziggurat (with the clue the PCs needed to find the artifact) because, quote "He was not accepting of Death." So the PCs dungeon-crawl the ziggurat, expecting to have a boss-fight with a Dracolich well above their paygrade, and, instead, find, after much foreshadowing that could go either undeath or apotheosis depending on how you looked at them, including elaborate animate bass-relief traps and the like, they find The Great One, alive (surprise!), and in Temporal Stasis (a spell that, like Wish, has not been possible to cast since the Dawn War, yet, here's someone who cast it), rampant as in mid-battle above his hoard, which is secured by a possible-in-this-Age 'Stasis Vault.' The party extract the clue (and an astral diamond, and a magic 'grace ring' or two, I think it was) from the hoard and continue on their quest. But a couple of the players are just itching to take on that Dragon and claim the horde - a classic, pile-of-treasure hoard (though light on gold, because Mercury Dragons, I figure, feel like it clashes with their scales, plenty of silver and platinum, though).
So, they finish that quest and - in a
n-way battle amongst the 8 4e players who showed up that week, a crew of 2-bit-arch-mage(they could all cast freak'n Chain Lightning, 'kay) spelljammer elves, an elemental-chaos-raider Hellship, a /second/ factions of Devils ("Under the Terms of the Secret Alliance between our respective Lords Mammon and Belial, I invoke the clause of mutual aid! ...to the precise degrees therein delineated, etc, etc...") who had been, well, bedeviling the players at my wife's homebrew 5e table,
Her table's players, playing their 5e characters in their native system), and, oh, several of the Arch-fey of the Shadow Court, on the top branches of Sinhalese, on a night when the entire Court of Stars was in session down'stairs.' We ran it in both systems simultaneously, on a 4'x8' chessex mega-mat, that required tree of the FLGS's tables. We called it "D&D 9th edition."
OK, technically no PC was higher than 20th, but it was Epic.
And, of course, one of my PCS opened The Box.
Point is, there was this uberDragon. And, 3 or 4 levels after encountering it, they're in a more sandboxey kind of period, and deciding what to do... "hey, remember that Dragon...?"
So they return to the world full of Mercury Dragons and find a trio of dragonborn 'archaeologists' (actually a non-combatant Librarian, a Mercurial Assassin, and a Dungeoneer) representing a truce among the three most powerful modern dragons, who have cleared the Pyramid of undead and are cataloging (without touching, because that gets you trapped in Stasis) The Great One and His Hoard, and after a little negotiation, the Dragonborn, on behalf of their Draconic masters, agree to stand by while the party take on The Great One and try to claim it's hoard.
Now, the Great One is in temporal stasis in the last moments of life, having exceeded the greatest possible age even for dragons, and cannot possibly live more than a few minutes (that's a lotta ongoing damage). So the party get too clever by half, and scribe a circle of protection (worth noting: I'd years ago ruled that any attack across a circle of protection breaks it, seems obvious to me) around The Great One keyed to natural creatures (they're all fey), and a dragondaunt-shield Ward next to it, as a fall-back position. They've crafted a special magic weapon, too. The plan is to take down the Stasis Vault (an encounter-worthy challenge in itself), wait for the Great One to mostly succumb to his great age (ie Bloodied by the ongoing damage), then jump in and try to strike a killing blow with the special weapon (which'll set up something else that I can't ever recall right now).
They do, with much effort take down the Stasis Vault, releasing both hoard and dragon. However, 5 rounds (and 200 hps of unavoidable last-moments-of-life-damage later, The Great One has put itself back in stasis - but not the Hoard, the matrix of high-epic magic items that anchor it were tampered with).
So the walk off, or, actually, transport via multiple trips walking a portable hole through a teleport circle, with a dragon horde. A little over a hundred tons of it, nearly the cargo capacity of their ship, after replacing their ballast with it, as well!
That 'we made off with a Dragon's Hoard without having to fight the Dragon because we were just too clever by half' bit, that's CaW. (Really, the plan to kill it like that was CaW, but even CaW plans don't survive contact with a high-Epic caster.)
CaW is, of course, completely unsupported by 4e.