In this sobering book, Barry R. Posen demonstrates how the interplay between conventional military operations and nuclear forces could, in conflicts among states armed with both conventional and nuclear weaponry, inadvertently produce pressures for nuclear escalation. Knowledge of these hidden pressures, he believes, may help some future decision maker avoid catastrophe. Building a formidable argument that moves with cumulative force, he details the way in which escalation could occur not by mindless accident, or by deliberate preference for nuclear escalation, but rather as a natural accompaniment of land, naval, or air warfare at the conventional level. Posen bases his analysis on an empirical study of the east-west military competition in Europe during the 1980's, using a conceptual framework drawn from international relations theory, organization theory, and strategic theory. The lessons of his book, however, go well beyond the east-west competition. Since his observations are relevant to all military competitions between states armed with both conventional and nuclear weaponry, his book speaks to some of the problems that attend the proliferation of nuclear weapons in longstanding regional conflicts. Optimism that small and medium nuclear powers can easily achieve "stable" nuclear balances is, he believes, unwarranted.