Many of the cast members were up-and-comers making their Hollywood débuts (including a young Bud Cort, of “Harold and Maude” fame), and onscreen they each possess an appropriate feeling of unease, as though they really are a bunch of reluctant strangers who were randomly thrown together in a precarious context. The ebullient personalities from the television series are nowhere to be found. Altman’s ensemble completely disappears into their respective roles, and no one ever steals the show (though Kellerman comes gloriously close).

Stories emerged about Altman’s idiosyncratic, freewheeling methods. His approach on the set was like that of a jazz bandleader seeking to harness and ride raw inspiration, to capture lightning in a bottle—a framework that dared his cast toward spontaneity and serendipity. Altman encouraged improvisation from his actors at all times, leading to the film’s revolutionary style, with its herky-jerky manner and overlapping dialogue. “We were a long, long way from an ‘original’ screenplay when actors started speaking,” Sutherland told me. The pace is often slow, dry, and muddled, giving the film an almost Chekhovian feel. Characters mumble and drift in and out of scenes that seem to have no narrative forward movement, making it delightfully hard to tell, at times, what is even going on. All of this so infuriated Lardner that he ultimately told the director, “You’ve ruined my film,” and announced at the movie’s first screening that there was not one word of his that remained in it. (Lardner went on to win an Academy Award for best screenplay.)

An old show-biz maxim holds that one surefire way for a performer to hold an audience’s attention is to appear as though they are in possession of a secret. Altman’s entire film has this feeling. As the “Three Army Doctors,” Sutherland, Elliott Gould (as Trapper John McIntyre), and Tom Skerritt (as Duke Forrest), are sly and subtle. In their hands, Hornberger’s frat boys become hipsters. Their attitudes are droll, their responses to situations are all arched eyebrows and sideways glances. We can’t always hear what any given one says under his breath, but we sure want to. They project a caustic intelligence, their rapport is contagious without ever being cloying, giving the proceedings a slow-burn, subversive edge. Even at their misbehaving worst, we’d just kind of like to hang out with them. As Pauline Kael writes in her review of the film, for this magazine, “ . . . I don’t know when I’ve had such a good time at a movie. Many of the best recent American movies leave you feeling that there’s nothing to do but get stoned and die, that that’s your proper fate as an American. This movie heals a breach . . . ”

Mike Farrell, who played Captain B. J. Hunnicutt in the television series (a character that appears in neither the book nor the film), keenly recalls seeing the movie “M*A*S*H” during its 1970 release. Farrell was a young actor living in L.A. at the time, actively involved in the anti-war movement, and he remembers the film’s galvanizing impact, calling it “necessary” in the context of what was then happening in Vietnam. The movie struck a nerve. Amid its absurdity and black humor, it was a sharp commentary on the senselessness of war, and on the obliviousness of those charged with prosecuting it.

The “M*A*S*H” television series, inspired by Altman’s film, débuted in the fall of 1972, on CBS. Although not immediately a hit, the network believed in the show, and by Season 2 it had garnered a significant following. The show was by turns funny, serious, and innovative. It explored new narrative techniques, introduced verboten topics to prime time, and probed the psychology of its characters in ways that had not been seen on a television series before—all within the confines of a half-hour sitcom format. Altman despised it. In his director’s commentary for the film, recorded for the 2000 DVD release, Altman calls the show “the antithesis of what we were trying to do,” and claims not to know or like any of the people involved with it. (“Alan Albert, or whatever his name is.”) Gary Burghoff, the only featured actor to appear in both the film and the series, treasures both experiences, and told me that Altman’s resentment probably stems from the fact that the show’s popularity came to almost entirely eclipse the influence of his film. (Altman had no fondness for Hornberger’s novel, either, calling it “just terrible.”)

Unlike the book or the film, the television “M*A*S*H” rallies around the character of Hawkeye. As depicted in the book, Captain Benjamin Franklin (Hawkeye) Pierce is a bumpkin from Bumpkintown, Maine. One of Hornberger’s characters describes him as “an uncouth yokel.” The character is introduced as being in his late twenties, a former college athlete, married with two young sons, and an avid reader of Maine Coast Fisherman magazine. While Donald Sutherland had not exactly hit the casting bull’s-eye (Sutherland told me that he and Altman never discussed the Mainer accent called for in the screenplay—“heah” for “here,” etc.), he was arguably within range of the character, having been brought up in Nova Scotia and naturally quiet, unassuming, and laconic. When the producers of the television series recruited Alan Alda to play Hawkeye, they not only intentionally missed Hornberger’s target entirely but wound up in the woods somewhere.

“We needed an attractive, funny guy,” the show’s original producer and co-creator, Gene Reynolds, told me, “a leading man, a hero, someone who could carry the show.” Reynolds had seen Alda onstage in New York and was convinced that this was the guy. Alda’s Hawkeye is flamboyant, intellectual, and manic—almost always the center of attention. New York-y, even. Where Sutherland’s charisma is sneaky, Alda’s is all out front. It stretched the limits of plausibility to imagine him back home in Maine, building lobster traps with his dad, but, as Alda told me, “We weren’t doing the book, and we weren’t doing the movie. I don’t think that the somewhat depressed character portrayed in the film would have worked for very long in the show.”

The question is academic; Alda’s Hawkeye became (and remains) one of the most famous characters in television history. Like Alda himself, his Hawkeye is kind, articulate, and caring. In the show, Alda reacts as much as he acts. One of his greatest gifts as a performer is how well he seems to listen, a skill he says he learned early on in his career, in improvisation class. “The secret to good listening is simple,” he told me. “Unless I’m willing to be changed by you, I’m not really listening.”

The television “M*A*S*H” includes two hundred and fifty-six episodes. To be fair, shows produced in the pre-cable, pre-streaming, dead-ball era of television were not designed to reward binge-watching. As Burt Metcalfe, a producer who was with the show from beginning to end, told me, “When you do that many episodes, some are going to be really great, and some are going to be really bad.” Writers were not then expected to build careful continuity, overarching narrative, and granular detail into every episode, practices that have become de rigueur today. Once a show aired, it was gone, to be seen again only in syndication, by happenstance, and almost always out of order.