A documentary by Stanley Nelson. Rating unavailable.

Five decades before Black Lives Matter began the current round of agitation against police brutality, the Black Panther Party used the Second Amendment of the U.S. Constitution (the one that now helps get over 35,000 Americans killed every year) as a literal call to arms. In 1966, weapons-carrying patrols started shadowing white police in majority-black Oakland, California, where the movement started.

As detailed in this two-hour documentary, made for PBS by writer-director Stanley Nelson, the Panthers also filled a social function, serving breakfast to schoolchildren in some of the most impoverished areas of the U.S. Initially, local authorities were flummoxed by what to do about these beret-and-shades-wearing, leather-jacketed avatars of liberation, whose aesthetic stance was even more attractive (and coherent) than their rhetoric.

When FBI dictator J. Edgar Hoover declared the Panthers a graver threat to American security than the Vietnamese, then at the peak of their war against U.S. occupation, things changed. Along with the feds’ extensive system of agents provocateurs, increasingly militarized police were given carte blanche to carry out suppression and targeted assassinations across the country. The FBI also exploited the ad hoc group’s inherent disorganization, as recalled here by numerous survivors who lay out the growing rifts between party founders Huey P. Newton and Bobby Seale (the second of whom is still alive but notably absent from the present-day talking heads), and the charismatic Eldridge Cleaver, who eventually fled to postcolonial Algeria.

His widow, Kathleen Cleaver, and other female militants are on hand, but they make only passing mention of their leaders’ deep-seated misogyny. They certainly paint a clear picture of the cults of personality that finished off the party in the 1970s. Obviously, there’s more about America’s postslavery institutions and their resisters than can fit in a two-hour movie. But with the aid of an extra-funky soundtrack, Vanguard of the Revolution makes a good, fist-pumping start.