"The Gatekeepers" is one of the top contenders for the Oscar for Best Documentary Feature this weekend. It's likely to lose to "Searching for Sugar Man," but "The Gatekeepers" tackles a more pressing political issue: Israel and its opponents.

The men of the title are the six living former heads of Shin Bet, also known as Shabak, the Israeli clandestine security service. Think of it as Israeli's version of our FBI, but even more clandestine. The only Shin Bet employee whose name is known is that of its chief; every other worker is anonymous. And that director, who has his hand in every national security decision made in the country, answers only to the prime minister.

This is the first time these men have gone on record to discuss their work -- and, especially, the deep moral questions to which it inevitably leads. How director Dror Moreh got their cooperation is unclear. But though his film, consisting of interviews with only those six gatekeepers, is often one-sided -- though sometimes not in ways you'd expect -- it's always gripping and very often informative.

On screen
'The Gatekeepers'
» Rating: 2.5 out of 4 stars
» Starring: Ami Ayalon, Avraham Shalom, Avi Dichter
» Director: Dror Moreh
» Rated: PG-13 for violent content, including disturbing images
» Running time: 95 minutes

The agency, which formed in 1949 but really came into its own after the 1967 Six-Day War, is charged with investigating internal terrorism and espionage. Shin Bet has reportedly been successful in stopping 90 percent of all planned terrorist attacks. But the 10 percent it missed have been, of course, deadly.

All six men, it seems, started their careers as hardliners and ended them, after spending their days studying those who would kill them and their families, as something else. They all now see a two-state solution as the only one to the "problem."

Perhaps it was all the time they had to spend dealing with politicians. "As head of the Shin Bet, you learn that politicians prefer binary options. They don't like having three or four options," one says. Politicians like being faced with a simple yes/no, do it/don't do it decision. These men, in their work, themselves find all sorts of shades of gray.

"Let's say you're hunting a terrorist," one proposes. "You can get him, but there are one or two people in the car. You're not sure if they're part of his gang or not." We're all aware that such decisions about "collateral damage" must be made, but we don't truly understand the pressure. "There's no time. These situations last seconds, minutes at most." And it's always easier, he argues, for a politician to do something than for a politician to pass on an opportunity and do nothing.

There are plenty of surprises here, but the most shocking moments don't involve such scenarios, but the opinions of the men who faced them. Avraham Shalom, who ran the service for most of the 1980s, calls the country he served "a brutal occupation force, similar to the Germans in World War II." The "similar, not identical" that he adds doesn't do much to soften the blow. It seems it's only when they leave do they really get a chance to reflect on the decisions they've had to make -- and invariably, but counterintuitively, as they get older, their political opinions move from right to left.