ABSTRACT
Adopting collective security as the common policy of a group of states envisions three distinct occasions for decision: the initial commitment, choices made thereafter to adapt readiness to the ongoing world, and action chosen when a member invokes the initial agreement and calls for help. Given governments' obligations to their citizens, and the fact that future crises cannot be known in advance, there is an element of contingency in any claim to take "collective security" as policy. As a consequence, efforts to find out "whether collective security worked" in any prior episode, and in turn to assess "collective security" as a policy, are bound to mis-state the problem. But whether collective security "works" concerns how states actually act when confronted by crisis; the norm of acting in concert and appropriately remains powerful, even if governments fall short of the norm and so fail to achieve what collective security could have offered them.
