Hollywood has a tradition of producing epic war films — sweaty, blood drenched chaotic masterpieces that vividly capture the brutal madness, unrelenting chaos and cruel suffering of battle, while exploring the splintering effect it has on the human spirit.

'Tropic Thunder' is not one of those films.

Despite the giant fireballs; dramatic shots of Huey choppers flying over green jungles; a muscled, machine-gun wielding hero with headband; a crazy bald man; and that Creedence Clearwater Revival song on the soundtrack, this is a big-balled comedy.

The story of the film of the book of the heroic Vietnam rescue mission, it's told through the eyes of three self-absorbed stars. Fading action juggernaut Tugg Speedman (hello, Sylvester Stallone) needs a comeback hit. Australian thespian Kirk Lazarus is going all out for a sixth Oscar — even undergoing skin pigmentation surgery — with his portrayal of the Black Experience. And slapstick comedian Jeff Portnoy (hi there, Eddie Murphy) wants to be known for more than his onscreen farting.

But the project's a disaster — and not just because there's no TiVo in the hotel rooms. Five days into on-location shooting, the production's already a month behind schedule, prompting the desperate rookie director to throw his actors into the jungle and just film everything guerrilla style. Pity nobody told the warring locals.

It's an explosive situation matched by appropriately rapid-fire comedy. But the ammo runs out. Although Ben Stiller's a pro at stretching one joke into a 90-minute laugh fest — all his legendary 'Zoolander' really had was "models are dumb" — the battle plan doesn't work as well here. 'Tropic Thunder' has too much story to support a single observation — "people in the movie industry are self-absorbed" — and takes itself a little too seriously. With all the subtlety of a napalm attack, he pushes and pushes punchlines long after you've wet your pants — you can almost hear him asking "do you get it? do you? do you? do you?" — with the actor/writer/producer/director inadvertently becoming one of the very people he's lampooning.

This is no stinker like 'Envy' though. Stiller (as Speedman) has surrounded himself with a cast largely capable of injecting his zany — and not so PC — ideas with the necessary zing. The he's-so-hot-right-now Robert Downey Jr is simply on fire as the confused Lazarus ("I'm a dude playing the dude disguised as another dude"). The role of Portnoy fits Jack Black as well as a giant panda suit would. And a grizzled Nick Nolte has some surprises up his sleeves as the film's consultant. The real surprise though is Tom Cruise as the filthiest motherf***er this side of a used car salesman. Unsurprisingly he overstays his welcome.

But, then again, 'Tropic Thunder' really is more 'Apocalypse Later' than 'Apocalypse Now'.