IN "DANCES WITH Wolves," a frontier meeting between Union soldiers and Sioux warriors, first-time director Kevin Costner does what greater filmmakers would never have thought of.

He disarms you.

Making love, not war, with the Indians, Costner (with Michael Blake's screenplay) creates a vision so childlike, so willfully romantic, it's hard to put up a fight. He circumvents big-scale movie portentousness with straightforward, emotional storytelling and traverses most of the sentimental pitfalls with deftly simple humor. He even helps you forget this movie clocks in at just over three hours.

You're left entirely scalped by his gentle edge, rubbing your head for liking what you saw. But there it is, and there he is, naked buns to the camera, staring at the bewildered Lakota Sioux staring back at him.

He's John Dunbar, a Yankee soldier whose attempted suicide charge upon the enemy backfired, leaving him with a military decoration. Now a lieutenant, his request to see the last of the real frontier is honored and he's promptly dispatched to the dangerous, unchartered wilds of South Dakota to set up camp at Fort Sedgewick. The backup troops he's expecting, however, never arrive and he's left alone in majestic but unfriendly terrain.

Yet Dunbar is such a naif (and Costner's guileless screen persona embodies this perfectly), and so respectful of the wary braves who observe him, he opens up a rudimentary line of communication with them. Before long, he's speaking Lakota, learning exotic names such as Wind in His Hair, and showing the Sioux where the tatanka roam. It almost goes without saying that Costner (who the Indians dub "Dances With Wolves") will meet and fall for a local woman (Mary McDonnell), an adopted survivor of a slaughtered Caucasian family.

There's humor throughout "Wolves." When wide-eyed Costner makes his pioneering request, for instance, he's faced with an obviously deranged major (an amusing Maury Chaykin), who constantly refers to Costner as "Sir Knight." On the journey west, Costner, who is writing a journal of his exploits, is accompanied by an uncouth man (Robert Pastorelli) given to unconcealed flatulence. "Put that in your book," giggles the traveler, after another of his signature crudities.

"Were it not for my companion," intones an appalled Costner in voice-over, "I believe I would be having the time of my life."

Last, but not least, is the fine array of performances by Native American actors, particularly Graham Greene as Kicking Bird and Rodney A. Grant as Wind in His Hair. They imbue Costner's labor of love with the kind of subtle dignity the movie asks them for -- and deserves. DANCES WITH WOLVES (PG-13) --