ON THE EVE of the 50th anniversary of the Black Panther Party, founded in 1966, comes a new documentary to recount the movement's lively history.

And, while children of the '60s and '70s may find much that is familiar in "Black Panthers: Vanguard of the Revolution," most also will find something to discover in the film, assembled by veteran PBS documentarian Stanley Nelson.

He uses vintage photos and music to place the movie in time, and finds insiders and eyewitnesses to explain the unique excitement created by the Panther "brand" - from the outset so much more ferocious than the mainstream civil-rights movement. (Ericka Huggins talks of seeing the swaggering Panthers on television and dropping what she was doing at Lincoln University to join the BPP in California.)

That ferocity came from Oakland-based founder Huey Newton's crucial insight: that the Second Amendment (and additional Wild West California law) made it perfectly legal for black citizens to carry a gun. This the Panthers made it their business to do - large guns, slung over their shoulders, as they conducted high-profile surveillance of police, a means of preventing police brutality.

The practical effectiveness of this open-carry policy is debatable (police/Panther shoot-outs clamed several lives and accomplished little), but as a political maneuver it was shrewd - white Americans who cast gun rights as an unconditional and foundational element of "freedom" were obliged to grant that freedom to militant black activists.

Combined with the right of speech and assembly and a free press (the documentary also recounts the publishing of the Panther newspaper), the gun became a potent symbol and enabler of a larger social movement. And, of course, part of the popular iconography of the Panther - Afro, beret, leather jacket.

"Vanguard" also reminds us of the less celebrated Panther initiatives: health clinics and a free breakfast program for poor children that at its peak was feeding 20,000 kids a day. We see Panthers making common cause with poor, rural whites - a potential alliance that alarmed federal authorities.

"Vanguard" presents this non-violent activism as a lost legacy of the party. Guns, meanwhile, provided pretexts for violent police raids, during which prominent Panthers were killed.

These raids were enabled by informants recruited by the FBI under J. Edgar Hoover, who made neutralizing the Panthers a priority. He exploited the strained relationship between founder Newton and rising star Eldridge Cleaver, shown appearing on "The Mike Douglas Show" (!) with John Lennon. Cleaver and Newton competed for power with different visions for the organization - as we see in "Vanguard," the organization didn't need much prodding to implode.

"Vanguard" spreads its energy of a decade's worth of history, and certain elements feel underserved - Newton's descent into madness, Cleaver's exile in Algeria.

In the end, the Panthers effectively disbanded, and some 20 still remain in jail.

As for the guns, in the end they did much less to raise consciousness about police brutality than the mobile phone.

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