Matthew Harries
Matthew Harries is managing editor of Survival, and a research fellow at the International Institute for Strategic Studies (IISS).

The nuclear-ban-treaty movement has a problem. It is not so much that a ban will be useless, or that it will undermine the Nuclear Non-Proliferation Treaty—although those things might well be true. The problem is that, when one moves past abstract principles to what the ban will actually do in practice, the target of the treaty is clear: intentionally or not, it is an attack on the nuclear-armed democracies—the United States, in particular—and their allies to the near-exclusive benefit of Russia and China.

It is an uncomfortable point to make. A world without nuclear weapons would be, in the long term, a better world than today’s, and one hesitates to get in the way of those who are trying to reach that goal. But, with treaty negotiations about to start at the UN, it is time to be blunt about the practical implications of a ban, as opposed to its principled ambitions.

The main way for a ban treaty to achieve anything of substance is to throw grit into the bearings of U.S. extended deterrence. It could do so by various means. It might contribute to pressure to withdraw U.S. nuclear weapons from their NATO host countries in Europe, or at least pressure on those countries not to procure replacements for their nuclear-capable aircraft. More broadly, it might make it harder for NATO to present a united front against Russian nuclear saber rattling—a direct threat to existing global norms of nuclear restraint—by pitching the alliance back into fractious debates about the role of nuclear weapons, on which a delicate consensus has been reached in recent years.

As a leaked U.S. non-paper made clear in the run-up to the UN General Assembly vote to authorize the start of negotiations, a ban treaty signed by U.S. allies or partners could set up legal obstacles to carrying out extended-deterrence-related operations. This could affect not just NATO, but perhaps also East Asia especially, via a prohibition on the transit of nuclear weapons through national territory, airspace, or waters, and a prohibition on participating in nuclear planning or subscribing to nuclear doctrines.

The ban’s advocates also hope that it will affect nuclear procurement choices in France or the UK—especially the UK, where there is a tradition of effective disarmament protest, although even there the consensus around nuclear deterrence now seems fairly settled. What the ban treaty will not do, however, is encourage Russia or China (let alone North Korea) to disarm, or even to participate more actively in bilateral or multilateral arms control initiatives. How could it? Civil society movements in those countries will not be pressuring their governments to make reductions or to halt existing modernization programs. Moral pressure is not a guiding factor in Russian or Chinese decisionmaking on national security. The logic of a ban treaty, which relies on generating such pressure, applies to countries where there is a direct connection between activism and the making of nuclear policy.

Supporters of the ban might hope that enforced constraints on the nuclear-armed democracies and their allies will encourage restraint on the part of other, less democratic nuclear-armed states. But this argument willfully misunderstands the motives for Russian and Chinese nuclear armament. Those countries’ nuclear programmes are primarily driven not by U.S. extended nuclear deterrence per se—nor, it need hardly be said, by British and French nuclear modernization—but rather, in the long run, by U.S. conventional military strength.

A global nuclear restraint regime is badly needed—but it will have to be negotiated with the active participation of at least several of the nuclear-armed states. Meanwhile, there are other important existing initiatives, including the Comprehensive Nuclear-Test-Ban Treaty (which is still to enter into force) and a future Fissile Material Cut-Off Treaty (about which negotiations have not even begun), as well as potential new ones, such as limits on nuclear-armed cruise missiles. These important efforts could be starved of diplomatic oxygen thanks to the attention that will be devoted to the ban treaty. And, yes, the arrival of a ban is likely to make the NPT’s difficult politics even more fraught, undercutting the authority of a vital treaty.

In other words, a ban will not reduce the role of nuclear weapons in the international system—except, perhaps, by reducing the credibility of U.S. extended deterrence. That, in turn, could have its own pernicious side effects, including undermining the security of the Baltic states, encouraging North Korean adventurism, and lending weight to calls for U.S. allies to embark on nuclear-weapons programs of their own. Such steps would make a world without nuclear weapons even more distant.

It was probably a mistake, in hindsight, for the United States to have reacted with such hostility to the humanitarian initiative—a series of meetings convened by states and NGOs, beginning in 2013, on the humanitarian impacts of nuclear weapons. Many of the participants in those meetings were driven by legitimate concerns, and the U.S. boycott of the first two conferences only served to increase their frustration. But when the humanitarian initiative turned explicitly into a movement for a ban treaty, it was not surprising to see the United States put high-level diplomatic pressure on states, especially its allies, to stay out—nor was it wrong for the United States to do so. The ban, to the extent that it succeeds, is an attack on core U.S. security interests.

This explains the apparent contradiction that ban-treaty advocates are fond of pointing out: how can the United States and its allies argue that the ban will be both ineffective and harmful at the same time? The answer is that two different things are being measured. The treaty will not bring the world closer to being free of nuclear weapons, but it might help deliver a world in which the nuclear underpinning of the U.S. alliance system is less secure. Perhaps this is not a bad thing, one might say—but it is very different from the universal norm that the ban is supposed to advance.

In one sense, the election of Donald Trump was a gift to the ban movement. U.S. extended deterrence seems less attractive when it is Trump’s finger on the metaphorical red button. NATO, thanks in part to the U.S. president’s own ill-advised words, is ripe with divisions to be exploited. What’s more, the coming confrontation over Russia’s alleged violation of the Intermediate-Range Nuclear Forces Treaty will require NATO to have some serious backbone—even if the United States does not respond with new nuclear deployments of its own, which hopefully it will not. If I were a Russian policymaker, I would be enthusiastically cheering on the ban movement in private, while maintaining an appropriately scornful tone in public.

A final risk should concern anyone who has a stake in the global nuclear order. The new U.S. administration may use the ban treaty as evidence that it is right in taking a dim view of the multilateral system as a whole. The ban is in danger of vindicating the worst stereotype of the UN: that it is both hostile to U.S. interests and terminally unserious. One can only hope that an administration that is yet to make nominations for dozens of key positions is simply too distracted to take much notice. But, in any case, the fight will soon be on to prevent a wholesale U.S. retreat from the daily business of multilateralism—not just on nuclear issues, but in all policy areas. A ban treaty will not help in that fight, and it might just do some harm.

Matthew Harries is managing editor of Survival, and a research fellow at the International Institute for Strategic Studies (IISS).