It may not surprise when a documentary about the endless Palestinian conflict quotes a vexed observer saying that the Israeli Defense Force is “a brutal occupation force similar to the Germans in World War II.” There’s always some bleeding heart peacenik with a statement like that in his pocket.

In “The Gatekeepers,” those words are spoken by Avraham Shalom, who from 1980 to 1986 headed Israel’s internal security service, the Shin Bet. When he invokes the German army, he’s not indulging in hyperbole. Shalom is a Holocaust survivor and part of the intelligence team that captured Adolf Eichmann and brought him to trial. He knows firsthand what it means to live under a racist regime.

Director Dror Moreh’s extraordinary film interviews six former Shin Bet chiefs, who speak out publicly for the first time. They discuss their challenges, tactical successes and strategic failures with a candor that is almost unimaginable. The most influential security experts in Israel, who ran anti-terrorist operations for the last three decades, are clear-eyed, unflinching pragmatists. They unanimously hold their politicians culpable for failing to lead the nation to peace. Their consensus is that by slighting peace negotiations, continuing the occupation of the West Bank and permitting illegal settlements, Israel’s leaders perpetuated a violent crisis with no end in sight.

“The Gatekeepers” is a triumph of storytelling, a revealing view into the intricate shadow worlds of international espionage. It plays like tense drama, not a history lesson. Engrossing computer-generated visualizations of terrorist strikes and retaliatory counteroffensives create a feeling of you-are-there intimacy. Moreh offers a concise timeline of Shin Bet’s history since 1967. Unlike many documentaries, whose footage seems to have been tossed into the air and randomly reassembled when it hit the ground, every interview in “The Gatekeepers” advances the story. And a sobering story it is. Yuval Diskin, the thoughtful spy chief who headed Shin Bet from 2005 to 2011, carried out targeted killings of Palestinian militants. He talks of pausing later in mid-shave to ponder the eerie, “unnatural power” of taking lives in an instant.

Shalom revisits the 1984 scandal that caused his downfall. Two Arab guerrillas captured a Tel Aviv bus with 41 passengers. Shin Bet agents stormed the bus and captured the gunmen. After they were disarmed and their hands tied they were killed on the spot on Shalom’s orders. The summary execution shocked the nation’s conscience, and Shalom was ousted. He and the field agents left amid an unprecedented flurry of pre-trial presidential pardons.

The film also details Shin Bet successes against Palestinian insurgents and Jewish religious extremists, showing the painstaking analysis that precedes most lethal-force operations.

“We win every battle but lose the war,” says Ami Ayalon, security chief from 1996 to 2000. He quotes the military theorist Carl von Clausewitz: “Victory is the creation of a better political reality.” Until international leaders find the courage to forge those improved political conditions, lasting peace surely will remain elusive.