FROM the halls of Montezuma to the spores of outer space, they will fight our country's battles anytime, anyplace . . . The Marines, sweating and swearing and valiant as lions, engage "Aliens" in this hell-bent-for-leathernecks sequel to the 1979 thriller by Ridley Scott.

"Alien" was a classic of gothic horror, but "Aliens" is a blockbuster of epic combat, a high-powered, spine-tingling, interplanetary "Pork Chop Hill." Here, a few good men -- and in the year 2036, a few good women -- battle the blood-thirsty beings of the planet Archeron.

The knuckle-whitening story begins as Sgt. Ripley, the only survivor of the Nostromo massacre, is picked up in her escape pod. Fifty-seven years have passed and no word of the aliens has reached corporate headquarters. Her story is dismissed, her career is in shambles when she's given a chance to prove herself on a rescue mission to Archeron.

Sigourney Weaver returns as the resourceful Ripley, pale and shaken after her ordeal but a woman with the mindset of John Rambo. Sometimes she even looks like the palooka, sweaty, grimy and bristling with nuclear grenades. But she also is fetching in her space-age skivvies when the landing party awakes from hyper sleep for the "drop" to Archeron.

The commandos are quintessential gyrenes -- smart-mouthed, tattooed, bulging with bravado and biceps. Pvt. Vasquez, an amazon with a major case of penis envy, has the unit's biggest weapon -- a small cannon called the Smart-gun.

"Hey, Vasquez," cracks one of the guys. "Have you ever been mistaken for a man?"

"Have you?" rejoins the macho babe.

Raunchy one-liners relieve the fear of the unknown that menaces this mean, terrific team. Only the sequel isn't as shocking because we know a little about the monster now. "Aliens" can't top the original caesarean scene -- the monster tearing through the abdomen of its human host. But this time there are more parasites. If "Alien" was a cancer metaphor, "Aliens" is more like AIDS. There may be no defense, though there are plenty of skirmishes.

Then there's the red-blooded feminism. Basically it's "Rambo" for her, with Weaver's demeanor steelier than Stallone's. But she is a woman. And that means she's got to balance a career and mothering when she takes a spunky nine-year-old space orphan under her wing.

"Aliens" inherits its heroics from "First Blood Part II. Both were written by director James Cameron, acclaimed for "The Terminator," which he directed and cowrote with "Aliens" producer Gale Anne Hurd. They're supreme sci-fi aficionados, lending guts and gumption to this impassioned production.

As in the original, Cameron's space looks lived in. The computer banks are dusty and the troopers wear fatigues instead of silver-zippered suits. The monsters, in their many forms, are recreated with gooey veracity, plus there's a new queen bee ovipositing spores in the aliens' nasty nursery. Boy, do those things make a lot of slime.

It gets slippery for Ripley in a girls-only showdown with the alieness, despite the backing of formidable comrades: Michael ("Terminator") Biehn as a dashing corporal and Lance Henriksen as a valiant synthetic ("I prefer the term artificial person myself"). The vigorous and well-chosen cast also includes comedian Paul Reiser in his first serious role, as a corporate villain; and Al Matthews as the bull-necked sarge who moves 'em out to the rat-tat-tat-tat of the drums.

Except for the droid, they're characters you'd find in any foxhole from "Sergeant York" to "The Green Berets." The enemy is as merciless as the Nazis, as elusive as the North Vietnamese. All of it is set against the pristine starscape of deep space.

Cameron and company have made a sequel that is gripping and vital. The 2 1/2 hours fly by with this brave company, our imaginations sucked into the screen as if by a black hole. ALIENS (R) -- At area theaters.