“The Gatekeepers” is now playing at Sundance Cinemas. PG-13, 1:41, three stars out of four

The six men featured in the Oscar-nominated documentary “The Gatekeepers” all agree: the current political strategy in Israeli has been a failure, and the state needs to open constructive dialogues with Palestine and the other Arab states.

That those six men are all former heads of Shin Bet, Israeli’s internal security agency, the ones who have been implementing that strategy against the Palestinians, is striking.

Much like Errol Morris’ “The Fog of War,” Dror Moreh’s film is a sobering inside look inside history, at mistakes made and opportunities missed. In this case, it was the mistaken belief that Israel could occupy Palestine indefinitely, with a long-term permanent solution to be determined later. As one security head puts it, it was there job to keep Palestinian unrest at a “low flame” — 20 attacks per year instead of 20 per week — to give the politicians the breathing room they needed to pursue a solution.

But that solution never came. Instead, Moreh shows from the inside of Shin Bet how they saw the conflict got worse and worse — bus bombings on one side, targeted assassinations and interrogations on the other. It’s an endless cycle, with every victory only setting the stage for the next defeat. For example, Moreh tells the story of one “elegant” assassination against a Palestinian terrorist, in which a bomb was hidden inside the terrorist’s cell phone, and detonated remotely when he’s talking to his father. The bomb goes off, and one terrorist gets taken off the board. But then the others are enraged, and the attacks worsen.

“Gatekeepers” looks into several key incidents, including an incident in which two terrorists are beaten to death while in custody. (The Shin Bet head in charge at the time is cagey, telling Moreh he regrets that the incident happened — because a reporter was there and the story got out.) In addition to the interviews, Moreh uses a wealth of archival footage, from horrific images of terrorist bombings to eerily antiseptic satellite footage of a terrorist killed by a missile.

But perhaps the most dispiriting for the Shin Bet heads is when the agency also had to start contending with a far-right Israeli faction that wants to trigger a holy war by blowing up a Muslim shrine, the Dome on the Rock. And, in 1995, when a young assassin kills Prime Minister Yitzhak Rabin for signing the Oslo Accords, it’s a body blow to Shin Bet. Not only as an intelligence failure, but it’s a recognition that, as one head puts it, “we can win every battle and still lose the war.” One head quotes a Palestinian physician who tells him that, even as the Israelis use their superior firepower and intelligence, they can’t ever claim victory. For the Palestinians, he says, “Victory is to see you suffer.”

If there’s a ray of hope in the otherwise dispiriting history lesson of “The Gatekeepers,” it’s that these six men saw and know more about the situation than most, and they’ve come to the conclusion that peace is the only option.