A re-visit of past proliferation helps understand the dangers of the further spread of nuclear weapons. Notwithstanding the establishment of an international nonproliferation regime and occasional, selective, and sometimes vigorous, country-specific non-proliferation policies, the fight against the spread of nuclear weapons has not been recognized in the past as an overriding policy objective by the international community jointly or severally (introduction). It will be argued that is largely due an overly sanguine assessment of the consequences of past proliferation, which has been less benign than is suggested by the reassuring persistence of the taboo on the use of nuclear weapons (part 1). Future proliferation’s consequences appear all the more dire as a consequence of a misunderstanding of the past, which meshes in with new and worrying technical, operational and strategic developments (part 2). ‘Proliferation futures’ will be examined in this combined light of a flawed narrative and new developments, which may lead eventually to the deliberate or inadvertent use of nuclear weapons (part 3). In order to avoid such an outcome, policy recommendations will be flagged (conclusion).