During the tense days of the Cold War, the United States deployed many kinds of small-yield nuclear weapons in the field. The “logic” of the ladder of escalation led Washington to field nuclear landmines, anti-ship demolition mines to be attached to the hulls of ships by atomic frog men, and even close-range rocket-propelled nuclear weapons. We managed to avoid all-out nuclear war at each rung on the ladder through a combination of luck and careful efforts to avoid miscalculation.

Now, as the Trump administration develops its Nuclear Posture Review, the temptation of small nuclear weapons is back. The review will try to lay out for the American public and the world President Donald Trump’s views on what American nuclear weapons are for, when they might be used, and what kinds of and how many weapons are needed to carry out U.S. strategy. Some respected analysts and nuclear experts have suggested that the review once again consider the pursuit of new, smaller, and more usable nuclear weapons, despite the dangerous experiences with small nuclear weapons in the past and the fact that the United States already has a number of these weapons. These experts, increasingly and understandably concerned about Russia’s nuclear doctrine and its large deployments of tactical nuclear weapons, argue that the United States should enhance deterrence by threatening to use its own smaller nuclear weapons, and to make those threats more credible by building more of these weapons. The thinking is that this buildup will make adversaries believe the United States is more likely to use nuclear weapons, thus reducing the prospects of nuclear use altogether – an admittedly worthy goal.

While concerns about Russia’s threats are valid, new nuclear weapons are not the answer and carry with them significant risks and costs that the United States must avoid. Smaller, more usable nuclear weapons will do little to alter adversaries’ calculations or make the United States more successful in a war, and they make America less safe by increasing crisis instability between the United States and Russia.

While the specific circumstances may be new, the debate over small nuclear weapons is not. From the effort to develop high-radiation, low-blast neutron bombs in the 1970s to the “flexible response” doctrine that led the United States to produce thousands of tactical nuclear weapons, we have had these debates before. But for all the current discussions and analysis, there is no evidence that Russia’s or North Korea’s willingness to consider first nuclear use is based on the credibility or the size of America’s deterrent.

There is, however, a wealth of evidence, ranging from public statements and diplomatic engagement, that Moscow and Pyongyang threaten nuclear first use to compensate for their conventional inferiority. They know they would lose any prolonged conventional conflict with the United States and its allies. Their plans to use nuclear weapons in a conflict are designed to either produce a frozen conflict – akin to Ukraine – or to prevent the United States from bringing reinforcements to the battlefield in defense of its allies. Increasing the range of nuclear response options available to the United States will have no bearing on these countries’ fundamental concerns, and won’t change their willingness to consider the early use of nuclear weapons. Moreover, lowering America’s own threshold for nuclear use could further erode stability and increase the likelihood of the kind of conflict that might lead to nuclear use by enemies. The hard reality of America’s conventional military superiority is that regardless of its nuclear capabilities and even use, adversaries losing a conventional war with the United States may resort to nuclear use.

General debates are interesting, but specific scenarios are instructive. John Harvey’s recent article for War on the Rocks posits a hypothetical situation in which Russia, facing conventional defeat in a conflict with the United States and NATO, uses a small nuclear weapon to attack an airfield in a Baltic state, hoping to block America’s ability to bring forces to the battle. If the United States develops new weapons, and chooses to use them despite having conventional alternatives, it is worth considering how these weapons might be employed. One option might be for Washington to counter-attack the Russian base where the nuclear strike originated as punishment. This would require NATO to conduct a nuclear strike against Kaliningrad or Russia proper. The size of the weapon the United States used would not matter: Russia’s leaders would likely view the strike as a major escalation and would be under pressure to respond in kind against the U.S. homeland. This course of action threatens to trigger a massive escalation of a regional conflict and must be avoided, especially since America could still prosecute the war and defeat Russian aggression conventionally.

Another response option for the United States and NATO might be to use nuclear weapons in the European theater, perhaps against Russian troops in the Baltics or a third country, although it is not clear what military advantage that would bring. In this scenario the United States would be using nuclear weapons on the territory of sovereign European states, possibly even one of its own allies. This would hardly enhance alliance cohesion or America’s global position in the face of a Russian attack. A needless nuclear response would also keep Washington from gaining broad international support to oppose Moscow’s aggression against a sovereign European nation. Lastly, the United States can reinforce multiple airbases throughout Europe, meaning Russia’s attack would not prevent its eventual defeat by conventional means. The reality is that short of an all-out nuclear war, the United States does not need nuclear weapons to defeat Russia. Smaller weapons are no more usable or relevant than large ones in a regional conflict where Russia has used such weapons itself.

In the most likely scenarios, Russia has already attacked a NATO member — either because of miscalculation or as part of a new attempt to use hybrid warfare to undermine states on its periphery. Either Russia has assumed the United States will not protect its NATO interests (a fatally flawed assumption) or events have overwhelmed rational efforts to avoid a military confrontation. Harvey’s concern that the United States should take effective steps to deter Russia from ever getting to this point are valid. But conventional deterrence and close alliance coordination are the proven remedies to such threats — newer small nuclear weapons won’t prevent leaders from making bad choices. They did not stop Putin from invading Ukraine, for example, though Kiev is not covered by U.S. nuclear guarantees. Regardless, building a small nuclear silver bullet to deter potential Russian use is unlikely to prevent the outbreak of such hostilities, and will instead increase the risks of accidental or unintended conflict.

So new, small nuclear weapons don’t obviously enhance deterrence or bring any real military utility. We should also consider how Russia and other states would respond to a decision by the Trump administration to pursue new weapons. It will give Russia, China, North Korea, and others easy political cover to continue their own programs. They will likely do so anyway, but why should the United States legitimize these countries’ pursuit of such policies if doing so brings no military or deterrent advantage? Some American allies will also view pursuit of new nuclear capabilities as an admission that Washington doubts its own conventional superiority. Otherwise, why would it need to enhance its position with new nuclear options? Sowing doubt among allies about America’s commitment to defend them will bolster the case within these countries that they need their own nuclear deterrents.

There is no question that the global security environment has changed from when the 2010 Nuclear Posture Review found that the United States had no military or technical need to pursue new types of nuclear weapons. Russia’s outrageous and illegal behavior both in Europe and even inside the United States requires effective responses, as does North Korea’s continued pursuit of nuclear weapons and long-range missiles. The 2010 review’s forward-looking strategy to enhance U.S. non-nuclear deterrence options has made tremendous progress. Those new and growing conventional capabilities have proven effective in Europe and must be reinforced.

The credibility of the U.S. extended deterrent is clearly a serious issue that demands attention. Allies like South Korea and those in Europe increasingly question America’s commitment to their security, but this has much more to do with Trump’s inconsistent and counter-productive behavior than with the capabilities of the U.S. nuclear arsenal. Small nuclear weapons can’t fix this problem. Clearly, the United States needs to provide these states with more reassurance in the face of growing threats to their security. But if U.S. conventional capabilities are so threatening to adversaries that they have to threaten nuclear first use, that seems to be a pretty effective, and non-nuclear, way to preserve a deterrent and reassure allies. This path — enhancing conventional capabilities, including combat deployments, rotations, exercises, and missile defenses — is the way to counter nuclear threats.

Developing the ability to put smaller, more usable nuclear weapons on Russian territory in short order will also increase crisis instability. The risks of unintended or miscalculated escalation to the nuclear level will become even greater than they are today. Multiple presidents over generations have sought to reduce the risks of accidental nuclear war, and it clearly remains in the interest of the United States to make that possibility as remote as it can.

Advocates for increasing America’s reliance on nuclear weapons also routinely discount the risks and costs of these programs — both financial and political. It is increasingly clear that just paying for the current arsenal and its planned modernization will be a massive achievement.  Instead of adding to the rising bill of these programs by layering even more capabilities of questionable utility, policymakers should focus on how the United States is going to manage and afford its dwindling core deterrent capabilities as the financial demands for these programs continue to grow. Indeed, there is a growing debate on how large a modernization the United States should pursue as the costs continue to rise. On top of the dollar figures is the real and growing public concern about whether the president can be trusted with the authority to use nuclear weapons, and what his authority means for crisis stability. Any decision in the Trump administration’s Nuclear Posture Review to pursue new nuclear weapons will send the entire policy — including those parts that enjoy broader support in Congress — into a partisan political cauldron.  Even without such a controversial step, the massive and growing costs of the defense budget — which now include additional funding for missile defense — are going to be lightning rods for debates in Congress.  Already in doubt, the pursuit of new legs for all three components of the nuclear triad will be increasingly dim.  This may be true regardless, but adding the controversy — to say nothing of the financial cost — of new weapons seems unwise at best and dangerous at worst.

The United States has 4,000 nuclear weapons, some 1,500 to 2,000 on active deployment and available for use. The explosive yield of these weapons range from five kilotons (or 1/3 of the yield of the bomb dropped on Hiroshima) or less to almost 500 kilotons.  It is true that these systems are aging and the delivery systems in particular are reaching the end of their serviceable life times. Extensive investment in the nuclear weapons complex, however, has shown that the weapons themselves can actually be maintained for many decades beyond their original intended lifetimes and remain safe, secure, and effective. Life extension programs already underway can ensure the reliability and safety of these weapons for many decades more.

There is no clear case to be made that new weapons enhance U.S. security.  Instead, what we are seeing is doubts by some nuclear experts that rational American leaders would ever be willing to use the weapons in anything but the most extreme circumstances. This frustrates advocates who believe nuclear weapons should remain viable, even central, tools of statecraft.  Thus, they push for new nuclear weapons systems that are supposedly more “usable” because the United States would be more willing to detonate them on the battlefield. It is not a coincidence that many of those pushing for new weapons also believe that the United States should increase, not reduce, the role played by nuclear weapons in national security strategy — another debate likely to be sparked by the Nuclear Posture Review when it is released in early 2018.

Even if there is disagreement about the need for new nuclear weapons, nuclear experts share a common concern about the increasing risks of nuclear weapons use (by the United States, Russia, North Korea, and others). Many, but not all, agree that strategic stability between Russia and the United States is undermined by Russia’s nuclear activities: its violation of the Intermediate-Range Nuclear Forces (INF) Treaty and its increasing use of nuclear threats in more scenarios — including those involving  NATO states who participate in missile defense activities, indicating a lowered bar for Russian nuclear use. To be sure, it is a challenge to convince Russia not to consider using nuclear weapons against the United States in the face of massive conventional inferiority, but U.S. policymakers cannot solve this challenge by building new, smaller, more usable nuclear weapons.  Moreover, the pursuit of such capabilities has costs for both the effort to modernize America’s aging arsenal of strategic nuclear weapons and for its rapidly dwindling leadership on the global effort to prevent proliferation.  New weapons are an old idea, but with real costs for U.S. security. They should be rejected, if not by this administration, then by the Congress that will ultimately be asked to foot the bill.

This article was originally published in War on the Rocks