The incoming German government, rattled by the prospect of U.S. President Donald Trump withdrawing security guarantees, is preparing a fundamental readjustment of its defense posture. The new coalition of Christian Democrats (CDU/CSU) and Social Democrats (SPD) has already agreed to push for changes to the debt brake that would pave the way to dramatically higher military spending. Germany’s likely next chancellor, CDU leader Friedrich Merz, stated that “in view of the threats to our freedom and peace on our continent,” the government’s new motto needs to be “whatever it takes.”

A litmus test for how serious these efforts are is whether the new government will pursue a Plan B for a possible end to the U.S. nuclear security umbrella for Germany and Europe. Berlin needs an ambitious nuclear policy rethink that includes a push to recreate nuclear sharing at the European level—with the continent’s nuclear powers, France and the U.K.—to deter Russia and other adversaries. It is also essential for Germany to invest in civilian nuclear research to maintain nuclear latency as a hedge. Fortunately, Merz has signaled willingness to do both.

As part of NATO nuclear sharing, Germany hosts about 20 U.S. B-61 nuclear bombs at the Büchel airbase. For much of the past few decades, a majority of Germans were in favor of getting these nuclear weapons out of Germany. This was part and parcel of the German desire to exit everything nuclear, be it military or civilian. As late as mid-2021, a survey published by the Munich Security Conference found that only 14 percent of Germans favored nuclear weapons on German soil.

Russia’s invasion of Ukraine led to a dramatic shift in public opinion. In mid-2022, 52 percent of Germans surveyed for Panorama magazine expressed support for keeping or even increasing U.S. nuclear weapons in Germany. Russia’s attack against nonnuclear power Ukraine, which included the threat of using such weapons to deter Europe and the United States from supporting Kyiv, clearly left a mark on the German population.

In light of such threats, it seems that a majority of Germans have concluded that it is better to be directly under a nuclear umbrella. After Russia’s invasion, German Chancellor Olaf Scholz decided to pursue a 10 billion euro ($13.85 billion) deal with the United States to buy F-35s to replace the aging Tornado fleet that would carry the U.S. nuclear bombs stored at Büchel airbase. With this deal, Scholz sought to lock in U.S. commitments to German defense.

Of all recent German chancellors, Scholz probably pursued the closest relationship with the Washington. He tried to stick to this path even after the return of President Donald Trump to the White House. At the Munich Security Conference in mid-February, Scholz said: ​“We will not agree to any solution that leads to a decoupling of European and American security.”

That statement sounds decisive, but only if you ignore that the decision to decouple from European security lies in the hands of the United States. Berlin has no veto power here.

Scholz’s likely successor, Merz, strikes a very different tone. Before official results had been announced on the night of the Feb. 23 election, he stated: “My absolute priority will be to strengthen Europe as quickly as possible so that, step by step, we can really achieve independence from the USA.” Merz also said that it was unclear whether “we will still be talking about NATO in its current form” by the time of the bloc’s planned summit in June, “or whether we will have to establish an independent European defense capability much more quickly.”

Merz is convinced that this needs to include a Plan B for the possible end of the U.S. nuclear umbrella. The chancellor-in-waiting has proposed discussions with France and the U.K. on whether the two are willing to engage in a nuclear-sharing arrangement with Germany.

That is a sea change in the German debate. Former Chancellors Angela Merkel and Scholz had consistently ignored French President Emmanuel Macron’s offers to engage in a strategic dialogue on nuclear deterrence in Europe. In a televised address on March 5, Macron responded positively to what he referred to as Merz’s “historic call.” The French president said that he had decided “to open the strategic debate on the protection of our allies on the European continent by our [nuclear] deterrent.”

The Merz-Macron alignment provides a solid political base for discussions on Europeanizing nuclear sharing further. Of course, there are many obstacles, risks, and unanswered questions, as critics of these proposals in the German debate have been quick to point out.

It is easy to belittle “somewhat panicky policy suggestions” by an “increasing chorus of pundits and policy-makers from across the mainstream political establishment that fear US abandonment,” as German arms control researcher Ulrich Kühn has done. But given the havoc that the Trump administration has caused in only seven weeks, it is not “panicky” to think through a potential U.S. exit from the trans-Atlantic alliance. Not seriously pursuing a Plan B would be grossly irresponsible at this point.

A first requirement is a shared vision of a realistic political arrangement for Europeanizing extended deterrence and nuclear sharing. One option would be to recreate NATO’s nuclear planning group at the European level, with France and the U.K. as its nuclear anchor powers. To allow for U.K. participation, this should be done outside the formal EU framework. At its core, the planning group should include a handful of key European countries (Poland, Italy and Germany would be certain to be among). The EU could be collectively represented through the European Council president or the EU foreign affairs chief. Leaders of Germany and Poland have already expressed openness to concrete nuclear sharing arrangements, like having French capabilities stationed in German or Polish soil.

Of course, the final decision on any nuclear weapons use would remain with France and the U.K., as Macron also stressed during his comments on March 5. This mirrors the current arrangement with the United States. Members engaged in nuclear sharing would contribute financially to the burden of maintaining the French and British nuclear arsenal.

As early as 2019, Bruno Tertrais—one of France’s foremost nuclear strategists—discussed such an arrangement. Mindful of the obstacles, he also debunked some of the most common criticisms. For example, even combined, the limited French and U.K. arsenals would not be a full substitute for U.S. extended deterrence based on an arsenal many times that size. But that does not mean that a France- or U.K.-based deterrent would not be credible, per se. As Tertrais argued, “a small arsenal can deter a major power provided that it has the ability to inflict damage seen as unacceptable by the other party.”

It is also unconvincing to claim that a focus on Europeanizing nuclear deterrence distracts from the necessary investments in conventional deterrence (including deep precision-strike capabilities). Tertrais contended that Europeans simply need to pursue both. And yes, the U.K. does rely on Washington for key elements of its own nuclear arsenal. But the French capabilities are fully autonomous, which is crucial for credibility in light of a possible U.S. turn against Europe.

To claim that a push to Europeanize nuclear sharing would incentivize nuclear proliferation globally seems far-fetched. South Korea, Saudi Arabia, or Turkey will make their own determinations about going nuclear based on their own assessments of their security situations. And in the medium and long term, Germany and Europe also need to think about arms control and confidence-building measures with Russia.

Of course, Germans and others now looking to France and the U.K. for nuclear protection might ask themselves how stable and reliable these European nuclear powers are politically. That is a valid question. After all, in the U.K. Nigel Farage—the leader of the far-right Reform U.K. party—is making steady gains. France may be just one election away from having a president from a far-right or far-left party hostile to sharing the French nuclear deterrent.

That said, the only other option for Germany aside from a European nuclear umbrella would be to pursue its own nuclear weapons. At this stage, given the political fallout, the financial burden and the time that it would take to make a German bomb is not a cost-effective alternative. Yet, as a hedge, Germany needs to invest in maintaining nuclear latency—that is, having the basic capabilities in place to pursue its own nuclear weapons program in a situation where it is left with no other alternative.

To this end, Germany needs to recommit to civilian nuclear research—and that should be a no-brainer for other reasons in an age of energy-intensive artificial intelligence and the need to phase out fossil fuels amid ongoing climate change. A leading economy such as Germany simply needs to be at the forefront of civilian nuclear research.

During the early days of Trump’s first term, Merkel declared that ​“we Europeans must truly take our destiny into our own hands.” Yet, little to no action followed. Today, we are seeing the dramatic consequences of finally taking that statement seriously.

Merz is very much right to call for switching to “hoping for the best and still preparing for the worst.” However uncomfortable this might be for many in Germany, this strategy has to include a Plan B for nuclear deterrence.