The Treaty on the Prohibition of Nuclear Weapons (TPNW) entered into force on Jan. 22. While supporters such as U.N. Secretary-General António Guterres have praised this development as an important milestone in the struggle against the bomb, critics like the Trump Pentagon have argued that the treaty could undermine the unity and security of the North Atlantic Treaty Organization (NATO). But whether the TPNW becomes a problem for NATO is entirely up to the allies.

As always with the Atlantic alliance, much will depend on the United States. Excluding the option of America itself joining the TPNW, the Biden administration is left with two alternative strategies. The first would be to continue to resist and make an issue of the treaty, raising the dickens to deter allies from signing. The second would be to kill the TPNW’s supposed negative externalities with kindness, accepting the treaty’s emergence while seeking to make the best of it.

What is the TPNW and Why Does It Matter to NATO?

The TPNW was adopted by 122 states in July 2017 and prohibits any development, possession, and use of nuclear arms. Promoted by a transnational coalition of states and NGOs, the treaty is designed to give institutional weight to the vision of a world without nuclear weapons and, by extension, to build pressure for disarmament over the long term. Unsurprisingly, the nuclear-armed states and many of their allies have been skeptical of the treaty, arguing that it might delegitimize the policy of nuclear deterrence or foster “polarization” in the international community. While NATO officially supports the goal of nuclear disarmament, none of the allies have so far joined the agreement. This could easily change over the next few years, however, as a number of political parties and electoral coalitions in NATO member states appear determined to capitalize on strong public support for ratification.

NATO has referred to itself as a “nuclear alliance” since 2010, but the uniquely nuclear aspects of allied cooperation are in practice limited to the deployment of a combined 150 U.S. B61 nuclear gravity bombs to Belgium, Germany, Italy, the Netherlands, and Turkey, participation in the annual nuclear drill “Steadfast Noon” by the five nuclear hosts mentioned above and two or three others, a few relatively equivocal paragraphs in NATO’s policy documents, and infrequent, choreographed “consultations” on allied nuclear policy in the NATO Nuclear Planning Group and its subsidiary organs. Three members – Britain, France, and the United States – have their own nuclear arsenals. Each nation’s head of government enjoys “sole authority” over their country’s nuclear arms. Now they must decide what to do about the TPNW. With the United States remaining the dominant force in NATO, the diplomatic strategy of the Biden administration will be of particular importance.

Option 1: Raising the Stakes

Broadly corresponding to the general approach adopted by the Trump administration following the 2017 adoption of the Treaty, the strategy of raising the stakes would involve publically threatening allies and partners considering signature with various political and diplomatic reprisals (as Team Trump did with Sweden), to raise concern about verification arrangements and the TPNW’s alleged undermining of other disarmament instruments, and to frame the new agreement as “dangerous,” “destabilizing,” and “incompatible with NATO strategy.” This tack might help delay what some have described as the long-term “inevitability” of a NATO member joining the treaty – several allies are already under increasing domestic pressure to sign – but at a substantial risk. Indeed, the strategy has at least three significant downsides.

First, the repeated harping on purported negative externalities associated with the TPNW risks fostering self-fulfilling prophecies. After all, publically claiming that allied support for the TPNW will inexorably “undercut security in Europe,” “weaken NATO,” or generate exploitable “divisions in the alliance” is tantamount to sowing doubt about the United States’ willingness to come to the aid of allies that have joined the TPNW, thus emboldening adversaries and potential aggressors. Taking a stance perceived to be unnecessarily hawkish or hostile to nuclear disarmament and the TPNW could also serve to turn public opinion against NATO and the United States, thereby fostering the very division the opponents of the TPNW say they are determined to prevent.

Second, a strategy of opposition draws attention not only to the TPNW itself but also to America’s de facto opposition to what has effectively been a declared ambition of successive U.S. governments, namely a reduction in the salience of nuclear weapons and a strengthening of the norms constraining nuclear arms. Effectively declaring that a general security guarantee is insufficient – that the NATO security umbrella must be overtly “nuclear” – also sends a troubling signal to other states: to be secure in the twenty-first century, you either need your own nuclear arsenal or an express nuclear security guarantee from an ally with a large and flexible nuclear force.

Third, the persistent promulgation of a series of technical objections to the TPNW that former IAEA director Hans Blix has described as vicarious and “strained” weakens Washington’s credibility and ability to lead on other issues. In summary, raising the stakes around potential allied support for the TPNW is no doubt tempting as a means of dissuading allies from joining, yet it has detrimental impacts on other goals and inescapably increases the agony if or when the gamble fails.

Option 2: Playing It Cool

The alternative strategy – playing it cool – would invite Team Biden to reverse the Trump administration’s overt campaign against the TPNW, ceasing attempts at persuading others not to sign and playing down the alleged negative externalities associated with the agreement. While this strategy would be fully compatible with proclaiming that the United States itself will not sign the treaty for the foreseeable future, and that America will retain a “safe, secure and effective arsenal to deter any adversary,” the U.S. government would under this approach make it clear, tacitly or explicitly, that it will not punish or withdraw the general NATO security guarantee from allies that decide to join the TPNW. To do so, U.S. officials would simply make clear the United States’ enduring commitment to the security of each of its allies and to Article V of the NATO pact – irrespective of individual allies’ position on the legality of cluster munitions, landmines, nuclear arms, or other specific means of war.

This approach might hasten the process of at least some non-nuclear allies joining the treaty – some appear to have refrained from signing primarily due to concerns about U.S. reprisals – but would effectively do away with the prospect of the TPNW undermining meaningful military cooperation in NATO, undercutting security, or becoming a wedge between the allies.

After all, whether the security guarantee is sapped or military exercises are cancelled is largely up to the United States. Most TPNW-supporters in countries such as Germany, Norway, and Spain are eager to adhere in a way that involves as little disturbance to existing military and alliance arrangements as possible. For example, the Norwegian Liberal, Christian Democratic, and Center parties all combine explicit support for Norwegian signature of the TPNW with enthusiastic approval of NATO and the U.S. alliance, including through longstanding backing of Norwegian contributions to allied operations in Afghanistan and elsewhere. Few TPNW supporters in U.S.-allied countries are looking to cease participation in intelligence sharing, military drills, or joint military operations.

It’s important to note that, legally, such cooperative activities are compatible with ratification of the TPNW. As emphasized in the Oxford Commentary on The Treaty on the Prohibition of Nuclear Weapons, the agreement does not proscribe membership in alliances with nuclear-armed states or participation in joint drills or operations with such states so long as the state party in question stops short of actively “assisting” or “encouraging” the use or possession of nuclear arms.

Why Option 2 is the Better Path

Support for the TPNW is hardly radical or contrary to support for transatlantic cooperation. A number of former leaders in U.S.-allied nations have come out in favor of the TPNW, including two former NATO secretaries general. Former U.S. Secretary of Defense Bill Perry supports the agreement. According to former U.S. official Lawrence Korb, “If Reagan was still alive, he would be taking a leadership role, along with Pope Francis, in trying to get other nations, especially those with nuclear weapons to ratify the TPNW.”

The TPNW could even have some benefits for the United States over the long term. The overall aim of the states and organizations backing the TPNW is to weaken the prestige value of nuclear weapons and to over time build pressure for nuclear disarmament through the stigmatization of nuclear arms. On the one hand, such normative entrepreneurship could be interpreted as a long-term challenge to America’s strategic autonomy and, ultimately, the credibility of U.S. central deterrence. Evidently, any deterrent threat loses its credibility if its enactment is rendered unacceptable. On the other hand, the United States has repeatedly promised to reduce its reliance on nuclear weapons and to seek their eventual elimination. Owing to America’s conventional military superiority, a lower salience of nuclear weapons in global affairs would, all other things being equal, favor the United States.

Permitting non-nuclear allies to join the TPNW could also be of considerable value to those in a Biden administration who are eager to promote measures of nuclear restraint such as decreased funding for certain elements of the ongoing nuclear modernization effort, U.S.–Russian negotiations on further nuclear reductions, the phasing out of land-based ICBMs, or a shift to a no-first use or “sole purpose” nuclear posture. At present, the central argument against all of this is that America’s allies would never accept it. Indeed, virtually all observers, including industry-aligned hawks, accept that the United States does not need a first-use policy or enormous nuclear arsenal for its own national defense. These instruments are necessary, so goes the argument, to “reassure” unspecified “allies and partners.” Non-nuclear allies joining the TPNW would help take the sting out of this often-overegged sales pitch.

One more question remains: Would the TPNW effectively outlaw extended nuclear deterrence? While the TPNW does not prohibit the individual or collective use of force by conventional means, parties to the TPNW would be prevented from explicitly calling on the United States or other allies to use nuclear weapons on their behalf, for example in a conflict involving Russia. Yet ever since the 1950s, when the Soviet Union developed long-range nuclear forces capable of doing immeasurable damage to the United States, it has been widely acknowledged that, unless America’s own vital national interests or survival were at stake, no U.S. president would authorize use of nuclear arms against Russia. As former national security advisor and Secretary of State Henry Kissinger reportedly put it, “great powers do not commit suicide for their allies.” U.S. threats to use nuclear weapons in response to minor conflicts or conventional aggression in Europe are therefore not believable and consequently of little value as deterrents.

To the extent that extended nuclear deterrence has any credibility at all, this credibility resides, first, in the prospect that a U.S. president might on their own terms come to the conclusion that any use of a nuclear weapon by another state would warrant a nuclear response and, second, in the possibility that initially local conflicts could escalate to a point where America became fully invested. Yet U.S. allies’ ratification of the TPNW would not legally foreclose American use of nuclear weapons in either of these scenarios; adherence to the TPNW by Norway, Germany, or Spain would not prevent discretionary use of such weapons by the United States.

Shifting from an explicit “nuclear umbrella” to an unspecified “security umbrella” would arguably have little if any impact on NATO’s overall defense posture. Everyone – including those in the Kremlin – would know that the United States possesses nuclear weapons and that America might use them if its perceived national interests so dictated. It would, however, strip proponents of nuclear primacy and increased spending on nuclear weapons of access to the lazy yet potent argument that any step towards nuclear restraint would be incompatible with NATO’s status as a “nuclear alliance.” Basing NATO’s security on an unspecified, general security guarantee would also have historical precedent: In NATO’s early history, between 1949 and 1954, Denmark refused to allow explicit references to NATO use of atomic weapons in the alliance’s strategic documents. 


As long as allies stay silent, the most conservative forces in and around NATO and the U.S. military-industrial complex will continue to have free reigns to present America’s “allies and partners” as a monolithic bloc of countries that oppose no-first use and are desperate for the United States to spend hundreds of billions of dollars on new ICBMs, new “low-yield” nuclear weapons, new ground-launched intermediate-range forces, and new nuclear-tipped cruise missiles deliverable from the air and sea. In fact, for many TPNW supporters in U.S.-allied nations, the disinclination to have one’s country used as a rhetorical bludgeon in the service of nuclear vested interests is precisely one of the reasons for supporting the TPNW.

If a progressive U.S. agenda on nuclear weapons is to succeed, it needs allies, partners, and civil society outriders to push the envelope. Those eager to support such an agenda must help shift the political center ground, expand the scope of political action, and allow Joe Biden to continue being a moderate.

IMAGE: Anti-nuclear activists of ICAN (International Campaign to Abolish Nuclear Weapons) and other peace initiatives stage a protest with 51 flags of countries that ratified the UN Treaty to Ban Nuclear Weapons and a nabber reading “Nuclear weapons are forbidden! More than 50 states joined. Germany didn’t”, in front of the Chancellery in Berlin, on January 22, 2021. The UN Treaty on the Prohibition of Nuclear Weapons came into force on January 22, 2021. (Photo by TOBIAS SCHWARZ/AFP via Getty Images)