This article surveys current security challenges and identifies obstacles to effective global and regional responses and cooperation in an era when security has become increasingly divisible. The new situation is partly explained by the complexity and variety of security challenges, both traditional and new, and by the linkages between them. It argues that a new pattern of improvised, ad hoc and often case-specific security mechanisms has developed, which it calls Collective Conflict Management (CCM). The argument is illustrated by reference to cases of CCM where a wide range of actors—multilateral institutions at the global and regional levels, individual states or ad hoc coalitions, professional and commercial bodies, and non-governmental organizations—collaborate in an effort to manage specific security threats and challenges, bringing together a variety of relationships, resources and skills. The urge for collective action, rather than unilateral or single actor-led, is motivated by a number of factors and ‘drivers”, not all of them necessarily positive or constructive. The article concludes that the success or failure of CCM will depend in part on the severity of the problems it faces and in part on the motives and incentives behind collective responses. This new pattern raises interesting and important questions for the future of international security. While CCM may be untidy and lack clear norms and standards, in many cases it may be the best available in an increasingly fractured world.