Oleg Orlov began his career by protesting against the Soviet invasion of Afghanistan in the 1980s. At about the same time, he joined Memorial, Russia’s first and most important historical and human-rights organization—in Russia, the two subjects are organically connected—while it was still an underground, dissident operation. In the 1990s, Memorial emerged into the open and began publishing books detailing the mass arrests and murders committed by the Soviet Union. During the decade I spent researching the history of the Soviet Gulag, I ran into Memorial historians and activists all over Russia, including in their one-person “office” in Syktyvkar and in the spectacular museum, now dismantled, that they built on the site of a former concentration camp near Perm. Anne Applebaum: Russia has a new Gulag Memorial is dedicated both to revealing the truth about the past and preventing that past from repeating itself in the future. Its activists work in archives, but they also monitor human-rights violations in modern Russia. Orlov, who became Memorial’s co-chairman, worked especially hard to expose the horrors of Russia’s …