The US debate surrounding ballistic-missile defence is becoming increasingly polarized: advocates claim that these defences are essential to US security and should be deployed as soon as possible; critics argue that they upset strategic stability, encourage regional arms races, and therefore, will not work. What is lacking in the current debate is a quantitative analysis of how well defences would have to work to meet specific security objectives, and what level of defence might upset strategic stability. This paper argues that there is no immediate need to deploy US national missile defences because accidental or unauthorized Russian or Chinese attacks are unlikely, and because deterrence should mean that the risk of attack from emerging ballistic-missile states is acceptably low. National missile defence might be a useful insurance, but other defence needs are more pressing. However, if the US did deploy such a system, a modified Anti-Ballistic Missile (ABM) Treaty that allowed the US and Russia to deploy 100 interceptors at multiple sites around their territory should not pose a realistic threat to the retaliatory capabilities of four of the five declared nuclear powers.; This bo

Should the US deploy ballistic-missile defences? The arguments for and against are becoming increasingly polarised. This paper offers what is currently lacking in the debate: a quantitative analysis of how well defences would have to work to meet specific security objectives, and what level of defence might upset strategic stability.