On November 4, 1979, 52 American diplomats and citizens were taken hostage by revolutionary Iranian students at the U.S. Embassy in Tehran. It was up to President Jimmy Carter to resolve the crisis while simultaneously running a re-election campaign against Ronald Reagan. Officially, Carter stressed “diplomacy as the way to get the Americans released.” Behind the scenes, he was working on a rescue mission.

Oscar-winning documentarian Barbara Kopple tells the story of that mission, Operation Eagle Claw, in her latest film, “Desert One.” “[The plan] was very plain and simple,” Major William G. Boykin of Delta Force explains in the doc’s trailer, “bring home 52 American hostages.”

But that task was much easier said than done. The rescue team faced faulty intel, dangerous fog, and failing flight instruments during the mission. And, as Major James O. Roberts of the U.S. Army reveals, “There was never a full-out dress rehearsal” for Operation Eagle Claw.

“Desert One” features interviews with Carter, members of his administration, Special Ops members who carried out the operation, former hostages, journalists, and revolutionaries who participated in the 1979 takeover of the Embassy.

“‘Desert One’ is really about what you do when there are no good answers,” Kopple told us. “To me it’s much more heroic — and interesting — to see people who have ‘the guts to try,’ as one of the men who undertook the mission famously put it. They need to find a solution. They want to be the good guys.”

Kopple’s “Harlan County, USA” and “American Dream” won Oscars for Best Documentary Feature. Her other films include “New Homeland,” “A Murder in Mansfield,” and “Gigi Gorgeous: This Is Everything.”

“Desert One” opens August 21. It previously screened at TIFF and AFI Fest.