the Labour government decided to pursue like-for-like renewal of Trident, a decision that was reaffirmed by the Coalition in 2010. The thinking underpinning both decisions now needs to be re-examined. Since 2006, important things have changed and it is time for a more honest debate about the defence choices facing the country. It has become clearer, for example, that a set of long-term threats has emerged, to which deterrence, nuclear or otherwise, is not applicable: not only climate change, which can be addressed only through coordinated international action, but also cyber-attacks and nuclear terrorism. Attacks of both kinds will be difficult to trace. Since deterrence only works against those with a known address, it is not a viable strategy for meeting this category of threats. Recent research also shows that large-scale use of nuclear weapons by either the US or Russia would be suicidal, not because of a retaliatory response but because global agriculture would collapse as a result, leaving the population of the attacking country to starve. The same research shows that even a small-scale nuclear exchange between India and Pakistan would affect at least a billion people and usher in colder temperatures than at any time in the past millennium. These facts do not mean that nuclear weapons are totally irrelevant to all future security threats. The weapons may still play important psychological roles in inhibiting wars between major powers; our position is not, as a result, a unilateralist one. What these factors do mean, however, is that nuclear deterrence is decreasingly effective. We could pursue like-for-like renewal of Trident and still perish as a result of a nuclear incident not directly involving the UK. Deterrence is also increasingly risky. The number of nuclear weapons in the world has gone down since the end of the Cold War, but the bombs are now in some of the most unstable countries in the world. Loss of control is a major concern. If we allow current trends to continue, some of these weapons are going to get used.While it might make sense to invest a huge portion of the British defence equipment budget, around 25-30 per cent in 2020-2030, into a nuclear system that provides insurance against every eventuality, it makes less sense to invest so much into one that provides less and less insurance against a narrowing range of threats. Given unlimited resources, this would be less of a problem but since 2006 we have also experienced a recession. The defence budget is being cut and reductions in conventional capability are ongoing. This matters for a number of reasons. First, the cuts are occurring even as each new generation of equipment becomes more sophisticated and expensive than the last. The implication, given that no end to public spending cuts is in sight and that health and education budgets are ring-fenced, is that our military will continue to shrink in future. Second, defence cuts are under way and will continue in other allied countries on which we rely, such as the US, France, and elsewhere in Europe. Third, the military research budgets of many non-Western powers are increasing. While we have a clear technological edge today, the long-term trend is towards reduced Western technological superiority. In future, we will be able to rely much less on technically sophisticated but ever smaller forces to win conflicts. Fourth, Americaâ€™s pivot to Asia signals its reduced willingness to provide for the security of Europe. As Libya and Mali show, Europe must take more responsibility in future, and do so with less. Some of the supporters of like-for-like Trident renewal argue that anyone questioning the current approach is irresponsible. But in the circumstances outlined, Tridentâ€™s advocates also have serious questions to answer. They want to pour limited national resources into a increasingly ineffective nuclear system while being unwilling either to call for higher defence spending to meet conventional shortfalls or to scale back the UKâ€™s level of international ambition. They want a gold-standard nuclear deterrent while under-investing in everything else. Their approach will demonstrate to the international community that we intend to keep nuclear weapons on permanent deployment for decades while seeking to deny those weapons to everyone else. In the process, it will destroy any chance of building the broad-based international support required for a stronger non-proliferation and nuclear security regime. It also potentially sets the country up for a future Suez moment when, in the context of a crisis thought to threaten our vital interests, we will either try to intervene somewhere and fail or wonâ€™t try at all because we donâ€™t have the capability. Either way, as a country committed to internationalism and to the defence of our interests, we will be diminished. The choice before us, then, is not between a risky and a risk-free future. There are no risk-free futures on offer. Given the range of challenges before us and the limited resources at our disposal, if the Governmentâ€™s Trident Alternatives Review reveals an effective alternative to like-for-like renewal of Trident, such as stepping down from continuous at-sea deterrence and the building of fewer submarines, we should pursue it. This would continue our glide-path to reduced reliance on nuclear weapons for our security, and in the circumstances, make sound strategic sense.