In virtually every year from 1939 to 2012 – the period under review – the number of latent nuclear powers exceeded the number of states armed with nuclear warheads. The book distinguishes between partial and full latency, depending on the states’ capability to produce fissile material in laboratory gram quantities or enough for at least one bomb. Thirteen countries reached partial latency, ten made it to full latency, and another ten became fully armed nuclear weapon states. One, South Africa, dismantled its nuclear arsenal and joined the NPT. In analysing the conditions under which latency can be used to gain influence, Fuhrmann breaks new ground. Nuclear latency is no novel issue in the field of nuclear security and proliferation – although it has arguably been underemphasized – but Fuhrmann advances our knowledge in his systematic examination of conditions and ways in which latency can be used to influence international peace and security, enhancing stability or inciting insecurity. The book centres on three ways in which latency may yield political benefit: deterrence by proliferation, deterrence by delayed attack and deterrence by doubt. In deterrence by proliferation, countries threaten to build nuclear weapons if another state threatens to change the status quo. Delayed attack promises retaliation when an operative nuclear force is ready. Doubts about the adversary’s nuclear status can make a nuclear weapon power think twice for fear of retaliation or risk of failure to eradicate the entire programme. This book is an outstanding contribution to our knowledge about the nuclear age. It is impressive in its analyses, comprehensive in its scope and intriguing in the theory it presents. For better or worse, its relevance for international affairs is growing.