Funny an war – pacts popular culture. The combat in Afghanistan and Iraq has been a bloody godsend for documentarians, who have exploited its depth and complexities as a virtue: Amid the chaos, there lies a body of narratives far richer and more troubling than the long-disputed official script. Unbound by the compromises of mainstream news operations, these filmmakers have been able to dig in, filtering the experience through alternate prisms.

Yet, the same volatile and dynamic turf has proven to be a quagmire for Hollywood, which cranks out one jabbering, hand-wringing mediocrity after another. Rule of thumb: There are no good feature films about Iraq. “Lions for Lambs” isn’t very good either, even though its megawatt casting implies a pending, Oscar-caliber statement. Director Robert Redford may be the closest thing to a folk hero that American movies have given us — the Lord of the Sundance! — and his film resonates with populist purpose. Basically, it’s a 90-minute dialogue about America’s post-September 11, 2001, engagements that transpires as a pair of American soldiers face off against the Taliban, gravely wounded, after a new military operation goes awry in the remote, snowy mountains of Afghanistan.

Mr. Redford and screenwriter Matthew Michael Carnahan (who also penned the Middle East shoot-’em-up “The Kingdom”) intend a broad civics lesson in which everyone is assigned blame for what’s happened in the past six years: the government that lied about weapons of mass destruction, the press that gave it a free ride to pump ratings, and the passive public. Breaking news, huh? Unfortunately, the screenplay adds nothing new or insightful to the debate, as extremely well-paid actors perform Op-Ed Page karaoke.

Meryl Streep makes the most of this. She plays a Capitol correspondent with 40 years of service on her résumé who is summoned to a rising Republican senator’s office for a scoop. Slick Senator Jasper Irving (Tom Cruise) has masterminded a new game plan for Afghanistan and wants Ms. Streep’s Janine Roth to spin it on the air for him. Ms. Streep’s performance, as a slyly critical and tooth-sucking journalist, nearly makes Mr. Cruise watchable, as his character regurgitates the GOP’s present-moment mea culpas while arguing that maybe it’s time we take on Iran, too. Mr. Cruise can be awfully good in his hyper-confident and slightly psycho roles (the self-help guru in “Magnolia,” the hit man in “Collateral”). Here, he’s animatronic. You keep waiting for a fuse to blow and Yul Brynner’s voice to come out of Mr. Cruise’s mouth: “Nothing can go wrong, go wrong, go wrong …”

Meanwhile, in sunny California, Mr. Redford assumes his familiar avuncular posture as a college professor named Stephen Malley who tries to talk some sense into Todd Hayes (Andrew Garfield), a promising but neglectful student who has given up on political science. Privilege and cynicism have given Todd license for apathy. As a way of shaking him back to social consciousness, Malley tells Todd a story about these two students — one black, the other Hispanic — who were so committed to the idea of change that they enlisted in the military.

As flashbacks reveal, the young men are the same two friends imperiled by the Afghanistan operation the senator is trying to promote. And, well, you can see where this is going to go. Malley even hauls out a famous quote from a German general in World War I, whose admiration for the

English grunts slaughtered by his army was immense, particularly when compared with his distaste for their gutless superiors: “Never have I seen such lions led by such lambs,” he said. Think about that at the next kegger, kid!

Once again, the movie raises a familiar line. The soldiers, played by Derek Luke and Michael Peña, are disenfranchised sons of tough urban neighborhoods — naturally, the least-nurtured by society and the first to serve in combat. So what gives white-collar liberals, sitting back in their easy chairs, any moral high ground?

These themes already are being beaten to death on the presidential campaign trail, to numbing effect. While Mr. Redford is wise to attend to balance, even if only to bolster the screenplay’s inherent critique, the execution makes for neither engaging drama nor enlightening discourse. Everything is chewed over like an old stick of gum. And vigorously.