On April 5, 2009, U.S. President Barack Obama stood before a massive crowd in Prague and gave a soaring speech announcing his commitment to “a world without nuclear weapons.” In pursuit of that goal, he pledged to seek an arms reduction treaty with Russia, ratify the Comprehensive Nuclear Test Ban Treaty (CTBT), and convene a global summit to discuss the eventual elimination of nuclear stockpiles. He acknowledged that a nuclear-free world was unlikely to be achieved in his lifetime, yet his speech marked the first time a U.S. president had set out a step-by-step agenda for abolishing nuclear arms. It represented a sharp break from the approach of U.S. President George W. Bush, who had expanded nuclear missions and rejected arms control. Much of the world was elated. Nuclear disarmament was back on the global agenda. That September, the UN Security Council unanimously adopted a resolution endorsing Obama’s vision and strengthening various disarmament and nonproliferation measures. The following month, the Nobel Committee awarded Obama the Nobel Peace Prize, citing his call for nuclear disarmament. More than six decades after humanity first harnessed the destructive power of nuclear reactions, the only country to have ever used nuclear weapons was charting a path for the world to put the genie back in the bottle.

Fast forward to 2018. In the space of barely ten years, the dream of disarmament now seems more distant than ever. All the nuclear-armed states are devoting vast resources to upgrading their arsenals. The United States and Russia are leading the way, undertaking massive modernization programs that entail new warheads and methods for delivering them. China is steadily increasing the size of its arsenal and developing new types of delivery systems, including missiles tipped with multiple warheads. These are considered more destabilizing because they create an incentive for the other side to strike first in order to knock them out early in a conflict. India and Pakistan, locked in a dangerous rivalry, are also expanding and upgrading their arsenals. If current trends continue, the combined stockpiles of nuclear weapons in China, India, and Pakistan could grow by around 250 warheads over the next ten years, from about 560 now to more than 800. Meanwhile, several of these countries have adopted dangerously escalatory nuclear doctrines and loosened their rules on the use of nuclear weapons.

The dream of disarmament now seems more distant than ever.

At the same time, arms control agreements are unraveling. Joint reductions by the United States and Russia—which together hold more than 90 percent of the world’s nuclear weapons—have stalled as tensions have increased. On the multilateral front, the global effort to prevent the spread of nuclear weapons—enshrined in the Nuclear Nonproliferation Treaty, one of the most successful security treaties in history—is fraying. The NPT’s nonproliferation norms and monitoring procedures have helped stem the spread of nuclear weapons and are a key reason there are only nine nuclear weapons states today—many fewer than the “15 or 20 or 25 nations” that U.S. President John F. Kennedy forecast in 1963. But the bargain at the core of the treaty is breaking down. The states without nuclear weapons agreed to stay that way in exchange for a commitment to disarmament on the part of the states with nuclear weapons, and the nonnuclear states increasingly feel that the nuclear powers have failed to uphold their end of the deal.

Most disturbing, however, is a trend among some leaders to glorify the world’s most destructive weapons. Russian President Vladimir Putin and North Korean leader Kim Jong Un are again turning nuclear weapons into symbols of national power, describing their capabilities in public, parading their weapons in the streets, and even issuing nuclear threats. Then there is U.S. President Donald Trump. He has boasted about the size of his nuclear “button,” threatened that North Korea “will be met with fire and fury like the world has never seen,” and backed a massive program to expand the U.S. arsenal.

How did we get from the Prague speech’s “world without nuclear weapons” to where we are today? The answer is not simply Trump. For all his nuclear one-upmanship, Trump did not create the current crisis in disarmament and nonproliferation; he merely exacerbated trends that were already under way. Before Trump took office, rising geopolitical tensions, a resurgent Russia, arms modernization, and a hawkish Republican Congress hostile to international law and agreements had all conspired to impede further weapons reductions. Facing a tidal wave of opposition, Obama’s vision of a nuclear-free world got swept away.

Ever since the dawn of the nuclear age, the world has gradually developed a consensus that nuclear weapons are so destructive and abhorrent that it would be unacceptable to use them, a notion often referred to as “the nuclear taboo.” But the norms and institutions of nuclear restraint are unraveling. Arms control agreements are being torn up. Cooperation is being replaced by unilateralism. Restraint is being replaced by excess. Now more than ever before, humanity risks facing a future in which the nuclear taboo, a hard-won norm that makes the world a safer place, is in retreat.

THE VISION THING

Obama’s disarmament efforts got off to a good start. In 2009, he shelved a controversial plan from the George W. Bush administration to put ground-based strategic missile defense interceptors in Europe, replacing it with a more modest plan that was less threatening to Russia. In 2010, the United States and Russia concluded the New START treaty, a relatively modest but symbolically important agreement under which the two countries committed to reduce the number of their deployed strategic warheads by nearly one-third, to a total of 1,550 each. The treaty portended a new era of reductions. Soon after it was signed, the Obama administration convened the first of four global summits on nuclear security, which resulted in tangible improvements in the safeguarding of nuclear materials. In 2011, while warning that the United States would retain the ability to launch a nuclear first strike, the administration promised to develop no new warheads. Beginning in 2012, the Obama administration began to engage Iran diplomatically on its nuclear program, resulting in the Joint Comprehensive Plan of Action a few years later.

Obama also ushered in important shifts in thinking about nuclear use. His administration’s Nuclear Posture Review, released in 2010, substantially narrowed the conditions under which the United States said it would use nuclear weapons—only “in extreme circumstances,” to defend the vital interests of the United States and its allies. For the first time ever, the report explicitly endorsed the nuclear taboo: “It is in the U.S. interest and that of all other nations that the nearly 65-year record of nuclear non-use be extended forever.”

How did we get from Obama’s “world without nuclear weapons” to where we are today?

Yet Obama largely failed to achieve the lofty goals he laid out in Prague. There was no follow-up to the 2010 New START treaty. Despite his administration’s narrow nuclear doctrine, Pentagon planning remained mired in outdated Cold War nuclear strategies that emphasized first-strike capabilities. By late 2010, the Obama administration had signed off on a massive effort to modernize the U.S. arsenal, with plans to spend some $1 trillion on the development of a whole new generation of bombs and delivery systems. These included smaller, more discriminate nuclear warheads, which arms control advocates worried might prove more tempting to use. Pretending that this weapons buildup somehow constituted “disarmament,” as Obama administration officials regularly did, only caused nonnuclear states to grow more cynical about the United States’ commitment to the cause.

Most striking for an administration that had talked about the need for a “moral revolution” regarding nuclear weapons, the Obama administration refused to endorse a UN-organized campaign that sought to highlight the “humanitarian impact” of any use of such weapons. Launched in 2012 and inspired partly by the Prague speech, this campaign brought together civil society groups and nonnuclear states in a series of conferences designed to mobilize support for the elimination of nuclear arms. The United States, along with the other permanent members of the Security Council, mostly boycotted these meetings. Nevertheless, the campaign resulted in negotiations at the UN and ultimately a vote to adopt a total legal ban on nuclear weapons, a treaty that now counts 60 signatories. Supporters of the ban are under no illusions that the nuclear-armed states will sign the treaty anytime soon. Rather, the aim is to further stigmatize the possession and use of nuclear weapons. In snubbing the meetings that led to the treaty, the United States and the other permanent members of the Security Council likely missed an opportunity to steer the campaign away from an all-out ban and toward measures that, while still reducing nuclear dangers, might have proved more palatable to the nuclear-armed states.

WHAT WENT WRONG

Why was Obama largely unable to follow through on the promise of a nuclear-free world? The answer has a lot to do with deteriorating relations with Russia, the United States’ main disarmament partner. For Russian leaders, the George W. Bush administration’s withdrawal from the Anti-Ballistic Missile Treaty in 2002 marked the start of a new arms race with the United States—a qualitative one focused on new capabilities, rather than a quantitative one based on numbers alone. By 2011, Russia had begun modernizing its old Cold War systems, both strategic and tactical. It also started developing new weapons, including sea- and air-launched cruise missiles that can carry either conventional or nuclear payloads, and it conducted various military exercises combining conventional and nonstrategic nuclear weapons.

The mushroom cloud of the first test of a hydrogen bomb in the Pacific Ocean, 1952 U.S. Air Force/REUTERS

Things got worse after Vladimir Putin returned to the Russian presidency in 2012. Russian leaders had long objected to the eastward expansion of NATO and the deployment of U.S. ballistic missile defenses in Europe, but their obstinacy on nuclear issues shifted into high gear. (Obama, under pressure from hard-liners, showed little willingness to make any concessions on missile defense, other than to offer repeated assurances that the systems were not intended for use against Russia.) In 2013, when Obama proposed an agreement in which the United States and Russia would further reduce their strategic nuclear weapons, Putin didn’t bite, and the next year, he invaded Ukraine. Later in 2014, Russia pulled out of the 1991 Nunn-Lugar Cooperative Threat Reduction Program, through which the United States had assisted Russia with securing its fissile material to prevent the problem of “loose nukes.” Occasionally, Russian leaders made explicit nuclear threats against other countries, as when Russia’s ambassador to Denmark said in 2015 that if that country joined NATO’s missile defense system, Danish warships would become targets of Russian missiles. And in 2016, Moscow boycotted the Nuclear Security Summit, the global forum first organized in 2010 by the Obama administration. These were final nails in the coffin of the U.S.-Russian security relationship.

Yet Russia was hardly alone in blocking Obama’s nuclear ambitions; even U.S. allies got in on the act. NATO has 180 to 200 nuclear bombs based in Belgium, Germany, Italy, the Netherlands, and Turkey. Although some NATO allies, such as Germany and the Netherlands, had been enthusiastic about the abolition agenda, renewed Russian aggression eroded European governments’ support for reducing the role of nuclear weapons in NATO security policy. France, meanwhile, was always much more dismissive of Obama’s vision of a nuclear-free world and opposed discussing disarmament propos­als in NATO, fearing that its own nuclear arsenal would be dragged into the talks. Poland and the Baltic states worried about a resurgent Russia and did not support de-emphasizing nuclear deterrence.

U.S. allies stymied Obama’s nuclear goals until the very end of his tenure. In the summer of 2016, as Obama contemplated declaring a “no first use” policy, France, Japan, South Korea, and the United Kingdom lobbied against changes to the U.S. nuclear doctrine. In the face of rising nuclear tensions with Russia and North Korea, U.S. allies’ defense ministries worried that a “no first use” pledge might be perceived as weakness. The White House relented.

Obama also faced formidable domestic opposition to key parts of his arms control agenda—especially from hawks on Capitol Hill and in the Pentagon. In Congress, in exchange for Republican support of the 2010 New START treaty, Obama threw the GOP a bone of billions of dollars to spend on nuclear modernization, a goal that most Republicans felt was long overdue. The Republican-controlled Senate also opposed the administration’s efforts to ratify the CTBT, even though the treaty would lock in an area of U.S. advantage: the United States has little need to conduct nuclear testing, given its unmatched ability to simulate tests on supercomputers.

The Pentagon, meanwhile, was never really on board with Obama’s nuclear-free world. It remained committed to the belief that a large nuclear arsenal was necessary to retain allies’ confidence that the United States was willing and able to defend them. Both the Pentagon and the State Department opposed the UN’s humanitarian campaign as an explicit attempt to delegitimize nuclear deterrence, on which U.S. security and alliances depended. State Department officials, more enthusiastic than their Pentagon colleagues about the Prague agenda, nevertheless worried that the humanitarian campaign’s insistent demands for faster progress on disarmament detracted attention from the patient, step-by-step approach to disarmament they favored. White House officials wanted the allies to remained united in their opposition to a ban, and some officials worried that participating in the meetings would send the wrong signal and weaken allied unity. (Eventually, the United States did attend one meeting, in Vienna in 2014.) Yet even U.S. arms control officials admitted privately to me that, as the United States repeatedly failed to deliver on any of the vaunted steps toward disarmament, such as ratifying the CTBT or negotiating further arms cuts with Russia, the step-by-step approach was beginning to ring hollow.

The Pentagon was never really on board with Obama’s nuclear-free world.

Obama faced major international and domestic obstacles to pursuing his Prague agenda, but in truth, his policies were also undermined by internal contradictions. For one thing, it was hard to reconcile the huge modernization program with disarmament. Moreover, even as the administration was promoting its vision of a nuclear-free world, it ultimately gave priority to U.S. security, and the United States continued to rely on the threat of nuclear retaliation for its defense. One National Security Council spokesperson managed to capture the contradiction efficiently, telling a Washington Post columnist that the administration was “always looking for additional ways to achieve progress” on Obama’s Prague agenda, “while maintaining a credible deterrent for the United States, our allies and partners.” Hence, the administration had to oppose the humanitarian campaign, the very group working the hardest for disarmament.

Perhaps most tragic, Obama’s interest in disarmament was genuine and deep, dating back to his undergraduate days at Columbia University, when the “nuclear freeze” movement, a reaction to the Reagan administration’s arms buildup, swept through college campuses. During his senior year there, in 1983, he wrote a paper for a class on how to negotiate arms reductions with the Soviets and was even published in a campus newsmagazine writing about the “vision of a nuclear-free world.” By the time he became president, nuclear disarmament had been on his mind for at least 26 years.

THE NEW NUCLEAR EXCESS

Since taking office, Trump has ushered in a frightening new world of nuclear excess. The president has not only enthusiastically embraced Obama’s modernization program but also committed the United States to an even more massive expansion of its nuclear arsenal. Nearly every element of the U.S. nuclear arsenal is slated to be upgraded, at a mind-boggling cost of $1.7 trillion over the next 30 years. This includes $100 billion for an expansion of the intercontinental ballistic missile program, including 666 new missiles; the development of a novel, technically risky “interoperable” warhead that the Obama administration had put on hold; and 80 new warhead “pits” per year (a pit is the fissile core of a weapon). It also includes a significant increase in spending on developing, testing, and deploying new nuclear weapons. These changes were enshrined in doctrine in February 2018, with the release of the Trump administration’s Nuclear Posture Review, which calls for the development of two new warheads and expanded ways to use nuclear weapons. The United States is now pursuing the most belligerent arms buildup since the end of the Cold War.

There is little reason to expect Trump to pursue arms control talks. As president-elect, when asked about his proposal to expand the arsenal, Trump responded, “Let it be an arms race. We will outmatch them at every pass and outlast them all.” His national security adviser, John Bolton, has been a persistent critic of the New START treaty, which he has derided as “unilateral disarmament,” as have Republican hawks in the Senate. Although the Trump administration has so far maintained the New START treaty, which is set to expire in February 2021, it has yet to hold talks with Russia about extending it. If the treaty is not extended, the U.S. and Russian nuclear arsenals will be unregulated for the first time since 1972.

At the same time, Trump is taking a sledgehammer to the norms of nuclear restraint. The interviews he has given suggest that he has little understanding of nuclear weapons or their role in alliances, and there is little evidence that he cares about the norms of nonuse, nonproliferation, or disarmament. Trump has implied that Japan and South Korea should get their own nuclear weapons. He has not declared the United States’ legal obligation, as a member of the NPT, to pursue disarmament, something every other U.S. president has done since the 1970s. He also withdrew from the Iran nuclear agreement, dealing yet another blow to the nonproliferation regime. If Iran decides to tear up the deal and get back to work on its nuclear program, then an arms race in the Middle East would likely unfold. Trump’s decision also effectively eliminated the prospect of reaching a similar deal to restrain North Korea’s nuclear program, since Pyongyang now has little reason to expect any agreement to last. Furthermore, his erratic behavior and bellicose rhetoric have vastly increased concerns about a U.S. president’s unilateral ability to push the nuclear button. The media have even reported that Trump once asked a foreign policy expert what the point of nuclear weapons was if they couldn’t be used. For the first time since the end of the Cold War, the possibility that an American president might actually contemplate the use of nuclear weapons has become a terrifyingly real prospect.

A candlelight peace vigil in remembrance of the Hiroshima atomic bomb victims in Santa Monica, California, August 2013. Jonathan Alcorn/REUTERS

THE CASE FOR DISARMAMENT

The nonuse of nuclear weapons since 1945 is the single most important accomplishment of the nuclear age. Leaders must do everything possible to preserve this 73-year tradition. Despite the reversals since the launch of Obama’s Prague agenda, disarmament is still the right goal for the United States.

There are 15,000 nuclear weapons in the world’s arsenals, many on high-alert status. The risk of a nuclear launch or exchange started by accident or miscalculation remains high, and the consequences of even one such incident would be catastrophic. In fact, since the nuclear age began, there have been an alarmingly high number of nuclear near misses—­accidents or miscalculations that almost led to a nuclear detonation or nuclear war. The qualitative arms race now under way, which increasingly mixes conventional and nuclear capabilities in deterrence strategies, is raising the risk of nuclear use. The new technologies increase the likelihood that a conventional strike could provoke a nuclear attack, whether through misperception or miscalculation. The threat to incinerate millions of people in the name of national security is both bad policy and morally bankrupt.

Many have argued that nuclear weapons are the United States’ “instruments of peace,” that they deter major-power war, or that they are needed as an insurance policy. Yet one need not be a radical antinuclear activist to arrive at the same conclusion that former Secretaries of State Henry Kissinger and George Shultz, former Secretary of Defense William Perry, and former Senator Sam Nunn arrived at in 2007, when they went public with their belief that disarmament—working toward “global zero”—is in the United States’ interest. As these senior statesmen realized, nuclear deterrence comes with tremendous risks and costs. The arguments in favor of deterrence, if sometimes true, are not likely to be true in every case. What happens when deterrence fails?

The growing risks of a catastrophic nuclear war outweigh the uncertain benefits of deterrence for the United States. Given its overwhelming conventional military power, the only thing that can really challenge the United States on the battlefield is another country armed with nuclear weapons. That means that the United States would be better served by a world in which no country had these weapons.

It is true that given the current international political context, nuclear disarmament is unlikely for the moment. For now, all nuclear-armed states remain committed to nuclear deterrence. But they can still take steps toward disarmament. As a first step, they should recommit to norms of nuclear restraint. This could include taking weapons off high alert and starting a dialogue about adopting mutual “no first use” policies. The United States and Russia, for their part, should negotiate an extension of the New START treaty. Furthermore, the nuclear-armed states should find a way to engage constructively with the goals of the treaty banning nuclear weapons, rather than simply dismiss it. For example, they could offer more public transparency about how their nuclear war plans meet humanitarian criteria. Such steps could be part of an expanded effort—possibly organized by the UN—to hold all the nuclear-armed states accountable for the possible consequences of their nuclear doctrines and decisions about use. Finally, the way policymakers and diplomats think about “responsible nuclear states” should also change: it is time for that oft-used label to apply only to those states that have demonstrated a concrete commitment to disarmament.

After decades of arms control agreements, security cooperation, and a growing consensus about the unacceptability of nuclear weapons, the world is now headed in the opposite direction. Geopolitical tensions have heightened. New arms races have started. States have reverted to valorizing nuclear weapons. The nuclear taboo is weakening. But nothing about this is inevitable; it is a choice our leaders have made. Nuclear disarmament will have to be a long-term project. Today’s decision-makers may not be able to complete the task, but they have an obligation to pursue it.