Traditionally, the central problematic of the Westphalian states system has been how to counteract the so-called ‘security dilemma’, the tendency for states in a context of uncertainty to defect from cooperative arrangements if they perceive other states' security preparations as threatening (misperception; arms racing). As the states system became more centralized and the number of major players declined in the nineteenth and twentieth centuries, the nondivisibility of benefits—the dangers of potential defection (world wars; nuclear annihilation)—grew while states' incentives to defect increasingly necessitated control from the centre. The end of the Cold War, however, has reflected not a further centralization (nondivisibility) of benefits in the international system but (1) an increasing divisibility of benefits in a globalizing world economy and (2) the declining effectiveness of interstate mechanisms at preventing defection not only by states (‘defection from above’) but also by non-state, sub-state and trans-state actors (‘defection from below’). In this ‘new security dilemma’, the range of incentives grows for the latter to defect from the states system itself—unless coopted through the increased availability of divisible benefits. Furthermore, attempts to impose security from above (intervention) can create backlashes which interact with complex globalization processes to create new sources of uncertainty: overlapping and competing cross-border networks of power, shifting loyalties and identities, and new sources of endemic low-level conflict. In this context, emerging mechanisms of stabilization will be uneven, characterized by structural tensions and suboptimal performance.