Despite the rise of new security threats like terrorism, cyber-war and piracy, the terrible destructive power of nuclear weapons still hangs over the world. Discussion on further strategic nuclear arms reduction has tended to be dominated by the analysis of possible trade-offs between the US and Russia. But as the prospect of further cuts below New START levels is contemplated, increasing attention needs to be paid to the possible shape of a new, multi-power approach to nuclear restraint.

While restraint at low numbers goes with the grain of thinking in most nuclear states,...