Meryl Streep as Mother Courage in John Walter's absorbing, perceptive Theater of War.

There are documentaries that entertain and many more that educate, and there are plenty that grab you by the lapels and spout hummus-breath in your face about how you need to stop eating meat and trade your vulgar, barbarous combustion-powered vehicle in for a bike — today! Then there are the rare documentaries that prod you, subtly but insistently, to reexamine the way you’re living.

John Walter’s Theater of War is one of the latter and no, it’s not about third-world labor practices or animal rights or climate change or the war. Okay, well, actually it is about the war — and all wars— but not directly. What it’s directly about is a 2006 Public Theater production of Bertolt Brecht’s heart-rending play Mother Courage and Her Children. Brecht wrote this tale of the 17th century Thirty Years War during the early part of World War II, and it's a clarion work of drama so eloquent and prescient that to call it “antiwar” is to reduce it to something duller and more didactic than it is. To paraphrase the novelist and Brecht/Karl Marx scholar Jay Cantor — one the half-dozen major interview subjects who contribute to director/editor John Walter’s complex, absorbing film — the play “is pretty close to a howl of despair.” It tells us not that “war is bad,” but that “war is.”

Walter’s film benefits from the participation of Meryl Streep, who plays the eponymous Mother Courage, and who sums up the both the play and the film early on: “We all live off the war.” There are trenchant contributions from Tony Kushner, the Pulitzer-winner who penned the new English adaptation of Brecht’s 60-year-old play; Oskar Eustis, the Public’s puffs-on-a-cigar-while-cycling-across-the-Brooklyn-Bridge creative director; and Carl Weber, Brecht’s former assistant director. (Fun fact: Impressed into the German army, Weber surrendered at first opportunity and spent two years in an English POW camp, where with the permission of the British officers in charge, he organized a theatre company and staged plays.)

Kevin Kline was also part of the production, but we see him only during his costume fitting, and in footage from the final dress rehearsal. Sadly absent from the proceedings is cast member Austin Pendleton, who might have had something to say given that he is himself a better-than-good playwright. Even so, Walter’s film is complete without him.

But the unlikely star of Theater of War turns out to be Brecht himself, no matter that he was 50 years in the grave when this production of Mother Courage opened in Central Park. Walter even gets almost exclusive access to the longest section of film ever shot of the pioneering Marxist poet and playwright: It’s his 1947 House Un-American Activities Committee testimony, shot by Fox Movietone for the newsreels. Brecht had originally declared his intent to join the “Hollywood Ten” in their refusal to answer HUAC’s questions, but he ultimately chose a more slippery, and arguably more effective third path of deliberately worthless cooperation. HUAC was very concerned about the “revolutionary” poems and plays Brecht had written. Given that he was living in the Weimar Republic during the Nazi ascendancy, you wouldn’t think that a desire to overthrow that government would have struck our Congress as alarming, but those were the times.

The cameras were there in the hope of capturing another indignant, showy refusal. Instead, Brecht, puffing on a giant stogie, answered all the panel's questions. Every one of them.

Very . . . slowly. Haltingly. And in a thick German accent he’d affected to make it appear his English was much more limited than it actually was.

No one could say he hadn’t done his duty, but given the lack of verbal fireworks that other witnesses had brought, the newsreels had no use for the footage. It sat in the Library of Congress for decades until Walter pulled it out, revealing that in addition to his acknowledged genius as a playwright and a director, Brecht could be one hell of an actor, too. On Halloween 1947, the day after his Congressional testimony, he returned to Europe for the first since time fleeing from the Nazis to the U.S. six years earlier.

It’s a tribute to Walter’s skill that no prior familiarity with Brecht or Mother Courage is necessary to appreciate his film. If you’ve never read or seen the play, Theater of War probably will make you want to visit the library, but you won't you know, need to, because Walter presents a synopsis of the action so gradually you almost don’t notice it. He lets his interview subjects provide the summary in pieces, always in the context of a larger point about their personal experience of writing or staging or performing or teaching that scene, so the recap never slows the pace of the narrative about the production. Pretty slick.

Theater of War screened only once during SILVERDOCS, and I’ve been unable to find any information about how or when it might see a commercial release. But it's well worth remembering until it reemerges. By then, you'll all have read Mother Courage and Her Children, no? If you're a registered voter in a nation at war, you could do a lot worse.