Throughout history, dictators have constructed secret police agencies to neutralize rivals and enforce social order. But the same agencies can become disloyal and threatening. This book explores how eight communist regimes in Cold War Europe confronted this dilemma. Divergent strategies caused differences in regimes of repression, with consequences for social order and political stability. Surviving the shock of Josef Stalin's death, elites in East Germany and Romania retained control over the secret police. They grew their coercive institutions to effectively suppress dissent via surveillance and targeted repression. Elsewhere, ruling coalitions were thrown into turmoil after Stalin's death, changing personnel and losing control of the security apparatus. Post-Stalinist transitions led elites to restrict the capacity of the secret police and risk social disorder. Using original empirical analysis that is both rigorous and rich in fascinating detail, Henry Thomson brings new insights into the darkest corners of authoritarian regimes.