For every major military invention in human history, there has quite always been a countervailing technology. Nuclear weapons have, however, remained an exception. Ballistic missile defence (BMD) has, in recent years, emerged as a formidable means to defend against nuclear-armed delivery systems though yet to prove their total reliability. What does the advent of BMD mean for the nuclear revolution – will it make nuclear weapons obsolete or in turn lead to a new arms race among great powers?