Earlier this week, the New York Times published a story about several attempts made by Mr. Trump to pull the United States out from NATO. Today, The German defense minister, Ursula von der Leyen, published an op-ed in the NYT about why the world still needs NATO. I fully agree with her account.

The NYT’s story says that the military and foreign policy establishment in Washington made the president abandon the idea, but there is no certainty that he will not return to this issue in the future and change his mind, forcing the U.S. withdrawal from NATO. We’ve seen him denounce international treaties and agreements that had strong support from the U.S. political establishment and all the “adults in the room” have already left the White House. So, the uncertainty and almost strategic lack of predictability surely make everyone in the European chancelleries very anxious and unsure about what may happen.

A US withdrawal from NATO will basically mean the end of the organization in all but name. It will definitely have consequences that will go much further than the North Atlantic, Europe or the entire Northern hemisphere. It will undermine the already crumbling European security architecture and will create profound anxieties in many parts of Europe. Outside of Europe, U.S. allies in Asia, the Middle East, et. al. will start to question how much should they rely on the U.S. security guarantees. If this happens, we may see arms races in the Persian Gulf, South East Asia, Southern Asia, and Europe.

In the North Atlantic and Europe, the US withdrawal will create a defense crisis. NATO is a highly integrated machinery and the US is its main engine. Take this engine away and the entire thing crumbles. On top of that, we cannot even comprehend what effects this will have at a cultural and interpersonal level. NATO is not only a defense organization, but it is also the institutionalized version of a security community. The defense and foreign policy practitioners, diplomats, experts, and policymakers are entangled in profound, sometimes decades-long, interpersonal relationships. They are socialized in a particular culture and have a relatively cohesive worldview. A US withdrawal from NATO will put under pressure these communities of practitioners and the security community that underpins, culturally, the institutional framework. A withdrawal will sever the strong transatlantic social interactions that facilitate the reproduction of this community with each new generation.

In Europe, the US withdrawal will increase the relative power and influence of Russia in continental affairs. At the same time, we may also witness an increase in the cohesiveness of the remaining NATO members, especially those that are also part of the EU due to the sudden insecurity created by the power vacuum left by the US withdrawal. At the national level, policymakers are probably already thinking about what until a few years ago was unthinkable.

How can the European states react to such a historic and potentially catastrophic event? It depends, of course, on their size, relative power, and proximity to potential [perceived] threats (i.e. Russia). For countries like Spain or Portugal, a US withdrawal will have a highly reduced impact compared to the effects on the Central and Eastern European countries. For countries like Poland and Romania, a US withdrawal will be perceived as a historical event with potentially catastrophic consequences. Old memories from the interwar period will be resurrected and contingency plans will be made in haste.

But what contingency plans or strategies could the European countries implement in such a situation? There are probably dozens of options and I definitely don’t have enough time to analyze every alternative, but the European governments have probably already allocated resources toward assessing all the potentialities. In a world defined by anarchy, one of the main duties of any responsible government is to prepare for any situation. And I am sure that most European governments are already working on contingency plans. The most eloquent example is the resurrection of the Permanent Structured Cooperation (PESCO) in 2018, probably as a direct reaction to the security uncertainty created by Donald Trump’s comments about NATO’s obsolescence.

A potential Trump withdrawal announcement will start a race to the Kremlin. Every European state, from Poland to Iceland, from Malta to Finland, will want to improve its relations with Moscow, or at least to ease the existing tensions. That is not going to be good news for Ukraine, for example. We may even see some bandwagoning from countries like Hungary or Turkey. But at the same time, most of them will work toward building a balancing coalition. This will require the expansion of EU’s defense and security roles, especially through PESCO but may require some treaty changes, especially because a mutual-defense guarantee (Art. 5 of the North Atlantic Treaty) may be desired. There are speculations that in the undesirable case of a US withdrawal, the French and German armies may be unified shortly after, essentially making the first step toward a European Army.

In the end, such a withdrawal will be a catalyst for further challenges against the liberal international political order. The post-modern European state, defined, according to Robert Cooper (2003), by the inextricably intertwined foreign and domestic policy (the border between the international and the national are extremely fluid), shared tools of governance and a conception of security as disentangled from the control over territory or the balance of power, will gradually be replaced by a resurrected European modern state. The post-modern state is not strong enough to survive without the US security umbrella. Its own definition makes it unable to survive in a world still dominated by modern states. States that act and conceive social reality in different terms, who prize the Westphalian sovereignty and autonomy, who seek power or security in territorial and resource-driven terms.