Since the 1960s Olson-Zeckhauser’s (1966) analysis, its ‘exploitation of the great by the small’ has provided economists’ core model of alliance’s provision of security/defense. But with the end of the Cold War, countries’ allocative behavior has diverged markedly from OZ’s predictions for defense as a homogeneous pure public good voluntarily provided. This paper suggests a replacement for OZ, with the essential difference that ‘defense’ rather than being aggregated into their single public good is disaggregated into more realistic categories of self-insurance and self-protection.