One of the most riveting and liberating events of postwar life was the Soviet policy of glasnost, the Gorbachev-era explosion of media. The euphoria came not from the means of transmission but, rather, from what was being transmitted—and read, and heard, and seen. After decades of totalist censorship, after art, history, science, journalism, philosophy, and so much else had languished under the state, Gorbachev, particularly in the years from 1987 to 1990, unleashed everything. The thrill of this was unimaginable, David Remnick writes. Now, as Vladimir Putin sends troops into Crimea, he is, step by step, turning back the clock on information.