It's hard to imagine today, but during the 1970's, the United States was in a kind of chaotic, violent anarchy. Bombs went off every day in the early 70's, planted by revolutionaries. Police were targeted, banks were robbed, and a wealthy heiress was kidnapped and turned into an armed warrior. Responsible for all this violence were a handful of groups, like the Weather Underground, The Symbionese Liberation Army, and the Black Liberation Army, among others. We speak to an author whose new book is a fascinating, exhaustive history of these groups.