In the aftermath of the British vote to leave the European Union, it has become apparent that extricating the United Kingdom from decades of EU membership will be no simple task. Nowhere is this reality clearer than in the realm of nuclear security. With Scotland having voted to remain in the EU by a significant margin, First Minister Nicola Sturgeon of Scotland has stated that a second referendum on Scottish independence from the UK is highly likely. Among the many economic and policy questions that a Scottish move towards independence would bring about, perhaps the most important involves the fate of Britain’s Trident nuclear weapons system. At present, Trident missiles are delivered by the four Vanguard-class submarines based out of the Faslane naval base in Scotland. Many Scots find the presence of nuclear weapons morally objectionable and would prefer a policy that expressly prohibits the presence of nuclear weapons on Scottish soil, similar to that of NATO countries such as Canada, Lithuania, and Norway. In fact, in the case of a Scottish vote for independence, Sturgeon’s Scottish National Party has pledged to negotiate the removal of the Trident system from Scotland within the next five years. Unfortunately, however, there exists no other facility in the UK that can house nuclear missile submarines with appropriate security and maintenance considerations, and experts estimate that it would take decades and potentially billions of pounds to construct another. Even if an independent Scotland were to allow these nuclear forces to remain on its soil, the future of the Trident program is by no means set in stone. Despite the recent July 18 vote supporting renewal of the Trident program, its hefty estimated price tag of nearly 31 billion pounds combined with political dialogue questioning the fundamental need for a nuclear deterrent in the modern era have created an environment wherein an anti-nuclear movement led by Corbyn’s Labour leadership has continued to gain substantial traction. Further, technical concerns about the assuredness of the submarined-based nuclear deterrent resultant from the spread of unmanned autonomous vehicles have begun to call into question the wisdom of nuclear submarine modernization in an era where cheap unmanned systems could potentially be used to bring down multi-billion dollar boomers. The Trident system is a key operational component of the NATO deterrent architecture, and without an effective infrastructure to support Trident, NATO may find itself in the new, and unenviable position of relative nuclear weakness. However, given the inescapable reality that sensing technologies are improving at a record pace, it is conceivable that the traditional invulnerability of submarine-based deterrents could be degraded. It is therefore important that NATO think carefully about the future of these technologies, and determine a path forward that maintains present deterrence capabilities while enabling the assured delivery systems in the future. Such a task will inevitably require coordinated technological development (and sound financial commitment) from a substantial number of member countries. This reality points to one of the major takeaways from the Trident renewal debate – namely, that for NATO to continue fielding an effective nuclear deterrent system in a rapidly evolving technical ecosystem, such tasks as R&D, system building, and system deployment efforts must be coordinated amongst the various member countries to a degree never before seen. Thus, on the eve of the potentially major geopolitical shift caused by Brexit, it is crucial that all parties remember both how critical these expensive nuclear modernization decisions are to global security, and how making them in isolation can result in suboptimal outcomes that are, frankly, unaffordable in the high-stakes realm of 21st century nuclear deterrence.