Policy attention to date has focused predominantly on understanding the consequences of nuclear weapon detonations. The probability side of the risk equation, by contrast, is less well understood. Risk assessment and risk management warrant more attention. In response, this study seeks to contribute to the facts-based discourse about nuclear weapons by drawing on a range of expert perspectives. It explores various sources of nuclear weapon risk, from technological aspects to military strategy to political considerations, among others, and considers recent security developments of relevance. In disaggregating the causes and level of nuclear weapon risk, the study provides a foundation for further dialogue and information-sharing. It seeks to identify common ground for reducing the risk of detonation of nuclear weapons for any reason.