European defence has been a key issue since at least 1948, with the Treaty of Brussels between France, the United Kingdom and the three Benelux countries. At the time, the spirit of the signatories was still to guard against the threat posed by Germany, which was still fresh in people's minds (following on from the Franco-British alliance treaty of Dunkirk in 1947). But it was also increasingly aimed at responding to the threat of the USSR, which was tightening its iron grip on the eastern half of the European continent. As we know, this treaty was soon superseded by the Washington Treaty creating NATO, which is still, to this day, the political and military framework for European defence, coupled with that of the United States. Although the Brussels Treaty eventually disappeared, it survives, notably through the collective defence clause incorporated into the European treaties by the Lisbon Treaty.  The idea, the project and the hope of a European defence are still alive, although they have not yet been realised.

The war in Ukraine has changed the situation in several ways. Firstly, it places the question of war and peace firmly centre stage in Europe, an issue that had never completely went away, despite the end of the Cold War; however, it is now back at the top of the political agenda. Secondly, the war has led to profound unity in the response of the countries of the European Union to Vladimir Putin's open aggression against Ukraine, and the European Union has asserted itself as a major player complementing NATO and the United States. Finally, it raises the question of whether, should the United States change its policy on Ukraine following the presidential election in November 2024, Europeans would be in a position to take over assistance to Ukraine and move towards a genuine collective defence.

To address this issue, it is necessary to take stock of European defence, with its achievements and limitations, and to reflect on the conditions under which a shift towards a genuine European defence could be envisaged.

External operations: mixed success

European defence is often a topic that is poorly understood. Hidden behind a multitude of esoteric acronyms (PSC, EDA, EUMS, OCCAr, CARD, IEI, MPCC, CPCC, etc.), there are many misunderstandings. While the majority of European citizens intuitively approve the objective of European defence and a European army, few understand that NATO is still the foundation of that defence and why this is so. Even the concepts of defence and collective security, which are radically different in spirit, are the subject of confusion, which is not uncommon in declarations at the highest level. So, the first step is to clarify the situation.

European defence is a policy being developed by the European Union regarding security and defence issues. It was still in its infancy at the time of the Maastricht Treaty, which created the European Union and launched monetary unification. It was intended then (and still is) to be an extension of a common foreign policy, known as the Common Foreign and Security Policy (CFSP), and was therefore outward-looking. Defence policy came into being in 1999 under the name of the European Security and Defence Policy (ESDP) and was renamed the Common Security and Defence Policy (CSDP) by the Treaty of Lisbon in 2007. In fact, it covers three different dimensions, with both progress and obstacles compared with the Cold War period when NATO exercised undivided hegemony over European defence cooperation.

The first dimension — external operations — is still the primary purpose of European defence. There are two reasons for this. On the one hand, the ESDP/CSDP was the natural extension of a more united and assertive European foreign policy in managing relations with the world. Secondly, the post-Cold War geopolitical context (Gulf War, wars in the former Yugoslavia and other conflicts) justified providing the European Union with the capacity to manage crises. It was the French who always pushed for this politico-military ambition. They succeeded in breaking the British deadlock with the Saint-Malo Declaration of 4 December 1998, asserting that the objective of an "autonomous capacity for action, backed up by credible military forces", which led to the launch of the ESDP, the first military capability objectives and the first operations in Africa and the Western Balkans from 2003 onwards.

Twenty years on the results are mixed. The European Union has launched more than 30 operations since 2003, with 22 still in operation. This is significant and some successes have been of particular note. In the Balkans, the European Union has deployed two military operations, one in Macedonia (Operation Concordia, 2003) and the other in Bosnia (operation Althea, since 2004). The latter is the EU's largest ground operation, comprising 7,000 troops at its outset; it is ongoing and has been reduced to 2,000 soldiers. The European Union has also deployed police missions in the Balkans and a major "rule of law" mission in Kosovo with judges, police and customs officers. Numerous missions have been deployed elsewhere in the world: to monitor ceasefires in Georgia and Indonesia; to carry out ad hoc security operations in Africa (DRC, Chad); to provide military training or assistance almost everywhere (except in Asia and Latin America); to intervene in the Israeli-Palestinian conflict (surveillance of the Rafah border between the Gaza Strip and Egypt, police and rule of law mission to the Palestinian Authority). In the context of the war in Ukraine, the European Union has provided training for 40,000 Ukrainian soldiers.

Also noteworthy is the development of maritime security operations, an area in which the European Union, thanks to its many ships, can play an appreciable role (400 warships, a number comparable to that of the United States). Operation Atalanta, which has been deployed off the Horn of Africa since 2008, has so far succeeded in combating piracy in this strategic area. Successive naval operations off the coast of Libya have ensured compliance with the arms embargo to contain the civil war. The European Union has just decided to deploy a naval operation off the coast of Yemen to combat the threats posed by the Houthi rebels to maritime traffic in the Red Sea, which is crucial for supplies to Europe. There is also a reinforced maritime presence in the Gulf of Guinea. The number of ships involved in each of these operations is limited, but this is an area where European action could play an increasing role.

Through all these operations, the European Union has become a provider of security. Moreover, the “Strategic Compass” adopted in March 2022, the first strategic and programmatic text of the European defence policy, confirms these projection objectives through its first two axes: "act" and "secure". In particular, the Union has taken up the capability objective proposed by Josep Borrell of a deployable force of 5,000 men, a number comparable to that of the French intervention in Mali in 2013 (Operation Serval). But where the EU has proved particularly effective is in combining civil and military resources, enabling it to draw on the full range of its policies and tools for action to help third countries strengthen their security. This civil-military integration has been central to the CSDP since its inception, with Germany and the Nordic countries seeking to give it a significant civil dimension alongside the military one. It has even set an example for NATO, which in its 2010 Strategic Concept adopted the doctrine of the "global approach" to crises, attempting (unsuccessfully) to implement it in Afghanistan.

The truth is that there is also a dark side to this balance sheet, which shows the limits of European power. The number of personnel involved in EU operations is around 5,000, far below the UN's blue helmets (almost 100,000) or NATO's major operations (up to 130,000 soldiers for the ISAF[1] deployed in Afghanistan from 2003 to 2014; 40,000 international soldiers deployed on the Alliance's Eastern flank since the start of the war in Ukraine, which could generate a force of almost 300,000 men, comparable to the Russian force in Ukraine).

Most European missions are civil or civil-military: the European Union has equipped itself more with an armed branch for its development policy than with the power to intervene militarily. Moreover, all the military capabilities listed in the catalogue (the 60,000-strong force planned in 1999, the 1,500-strong "battle groups" planned since 2007) have never been mobilised, and the same is likely to be true of the new 5,000-strong force. This ambition has been curbed because Europe is reluctant to become actively involved in conflicts, i.e. to wage war. In theory, it could conduct "combat force operations for crisis management" (art. 43-1 TEU), but in practice it does not. Even the latest naval mission launched in the Red Sea is intended to be defensive. For this reason, the French flirted for a while with a smaller format, the European Intervention Initiative (EII), launched in 2018 bringing together thirteen countries, but the rout in Mali put an end to the coordinated deployment of European special forces between 2020 and 2022 (Takuba force), the first concrete attempt to implement the EII.

Europeans prefer to rely on American power and NATO for the most ambitious operations (intervention in Libya in 2011, intervention in Afghanistan), or on Member States prepared to act alone (like France in Mali). Even where the European Union deploys troops on the ground, as in the Balkans, it does so within an essentially Atlantic framework. The Althea mission in Bosnia has taken over from NATO and continues to be run by a NATO chain of command. And in Kosovo, NATO continues its mission (with almost 5,000 troops), since conflict is still latent there with Serbia refusing to recognise the independence of the province.

Armaments cooperation: steady progress but far from the target

The second dimension of European defence is armaments cooperation. Like CSDP operations, this dimension only really came into its own after the end of the Cold War, even though the WEU[2]  had attempted to initiate a form of armaments cooperation. Cooperation during the Cold War remained very limited (e.g. the Hot and Milan missiles and the C-160 Transall aircraft between France and Germany) and then developed somewhat (the Eurofighter combat aircraft, the NH90 and Tiger helicopters, the A400M transport aircraft, the Franco-Italian Horizon and FREMM frigates with their Aster missiles, the Meteor missile and the Male drone).

The inadequacies of European armaments cooperation have been clearly identified in recent years. The 27 Member States spend three times less than the United States on defence, but they have six times as many armaments programmes. They do not benefit from the economies of scale of a unified budget, nor from large-scale programmes. This has not prevented some fine successes, notably by the French defence industry, which (taking advantage of Russia's weakening) managed to become the world's second-largest arms exporter by 2023, with the Rafale fighter jet in particular.

The Europeans have created a number of tools to encourage cooperation, in particular the Organization for Joint Armament Cooperation (OCCAR) in 1996, which is used to manage the major programmes developed jointly, and the European Defence Agency (EDA) in 2004, which is supposed to act as a catalyst for joint initiatives but has only a very limited budget (barely €40 million).

It was particularly from 2013 onwards that the European Union, at France's initiative and taking advantage of the United Kingdom's departure, stepped up its cooperation efforts. Directives have restricted the scope of the exemption in Article 346 TFEU, which in principle excludes arms and war material from the free trade rules of the internal market. Following a "preparatory action" launched in 2016, a European Defence Fund was set up with €8 billion over the period 2021-2027 (i.e. more than €1 billion a year) to finance joint military research and capability development projects. This is not a large amount compared with the sum of military budgets, which remain national, and it does not avoid the criticism of being spread too thinly, but it should encourage the development of cooperation.

The war in Ukraine has provided new impetus. Europe has financed arms deliveries to Ukraine through its "European Peace Facility" (whose budget has been increased to €12 billion): this is only part of European military assistance, which is mainly based on bilateral transfers. It has also financed a plan to increase Europe's annual ammunition production capacity to 1 million, and has set up its own instrument to finance the joint procurement of equipment by Member States in a bid to encourage pooling.

The third axis of the 2022 "strategic compass" is entitled "invest". All in all, the 27 Member States have increased their military spending by 40% since 2014, and most will have exceeded the target of allocating 2% of their GDP to defence by 2024. However, there are a few caveats. This 2% target was set by NATO in 2014, after the first Ukrainian crisis: everything is happening as if the strategic objective of rearmament were an Atlanticist objective, both to counter the threat from Russia and under pressure from the United States, which spends more than Europeans on defence proportionally to its GDP and wants to see Europeans increase their budgets and take their share of the burden ("burden sharing", which was already the order of the day during the Cold War), in particular by buying American equipment. 

Furthermore, the European defence industry remains fragmented and defence cooperation is still managed on an intergovernmental basis. There is no coordinated planning of equipment procurement policies, despite certain consultation processes (CARD, coordinated annual review on defence). The major structuring projects of the future (European combat aircraft, European battle tank) have not yet been launched. In an area that remains central to national sovereignty, the degree of national control (armies, armament delegations) remains extremely high, and this is inevitable. 

The European Union is now playing a role that it did not assume during the Cold War and, if the trend continues, we can expect a number of favourable factors to converge: coordination, joint research and production, economies of scale in orders. The combination of the intergovernmental method, which is unavoidable when it comes to an area as sovereign as defence, and "Community" pooling, through jointly managed funds and programmes, also means that defence could lead to new successes comparable to those achieved in aeronautics (Airbus) and space (Ariane, Galileo, Copernicus).

Collective defence: a mission reserved for NATO

That leaves the third and most essential dimension of European defence: collective defence. This is NATO's preserve however. The difference between collective defence and collective security should be borne in mind.

Collective defence is an alliance which, under Article 51 of the United Nations Charter, is authorised in its defensive function (the "inherent right of individual and collective self-defence"). It is on this basis that alliances such as NATO and mutual defence commitments exist. And apart from the Collective Security Treaty Organisation, which brings together Russia and a number of post-Soviet countries, the network of alliances in the world remains focused on the USA.

Collective security is different: it is inclusive (it does not follow the logic of blocs) and it is based on common rules accepted by all, in particular the non-use of armed force, respect for territorial integrity, the right to self-defence, and mechanisms for collective response to an aggressor who threatens international peace and security. Collective security is ensured within the framework of the United Nations, with a right of veto granted to the major powers, permanent members of the Security Council. For the transatlantic area ("from Vancouver to Vladivostok"), the OSCE, is only a reduced form of collective security because it lacks executive mechanisms (and the rule of consensus has largely paralysed it).

The European Union is neither an alliance nor a collective security organisation (because it is not inclusive). It was the Atlantic Alliance, created in 1949, which formed the framework for Europe's collective defence during the Cold War, in the face of the Warsaw Pact, and after the Cold War, updating its missions (1991, 1999, 2010 strategic concepts), expanding to include the new democracies of Central and Eastern Europe. The European treaties state that NATO is "the foundation of the collective defence" of its member countries, and this is reiterated in the "Strategic Compass" adopted in 2022 (that is why its fourth axis is called “cooperation”). It was also within the framework of NATO that military reassurance measures were taken, after 2014 and even more so after 2022, to protect the new Member States on the eastern flank (the Baltic States, Poland and Romania) from the growing Russian threat. Finland and Sweden preferred to join NATO after the Russian aggression against Ukraine, rather than remain within the ambiguous framework of the European Union. NATO has deployed 40,000 allied soldiers (mainly Europeans, including 2,000 French) to reinforce the defence of its eastern flank.

The war in Ukraine has further increased NATO's domination of the European strategic landscape, even though this never ceased to be. In particular, the Alliance guarantees the coupling of Euro-Atlantic security through the deployment of American troops in Europe (their numbers fell to less than 70,000 after the end of the Cold War but have now risen to 100,000) and also through the deployment of tactical American nuclear weapons (B-61) in several Alliance countries (Germany, Belgium, Italy, Netherlands, Turkey). All experts in strategic affairs know that NATO is where the real action takes place, where European armies ensure their interoperability with American power, where allied defence is integrated by a powerful structure (7,000 people, notably in the Mons headquarters), and where defence plans are prepared to guarantee European defence.

Although European defence has progressed in terms of operations and cooperation on armaments, it does not guarantee the defence of Europe. However, Europeans do have a collective defence article (Article 42-7 TEU) inherited from the collective defence clause in the Brussels Treaty. Although this article is a reminder of NATO's pre-eminence, it has the merit of existing. It has been used once, for the benefit of France after the attacks in 2015, just as Article 5 of the Washington Treaty was used once, for the benefit of the United States after the attacks in 2001 (it was the basis for the Alliance's long intervention in Afghanistan). Article 42-7 did not give rise to any robust, formalised intervention by the Union alongside France in Mali or against Daesh, but it should be noted that this article has been preferred to the solidarity clause in the event of a terrorist attack or natural disaster (Article 222 TFEU) and that several Member States have wanted to step up their commitment alongside French (and allied) troops in operations against Islamic terrorist movements. The collective European defence clause has even been supplemented, in the Treaty of Aachen (2019), by a bilateral Franco-German defence clause, which is supposed to coordinate with the European Union and NATO clauses.

The possibility of an American withdrawal from NATO weighs heavily on European strategic thinking, particularly in view of Donald Trump's potential return to power. Admittedly, the election has not yet taken place. And Trump, who has a talent for making provocative statements, has not so much announced the withdrawal of the United States from NATO as he has sought to put pressure on Europe to increase its financial contribution. Despite tendencies towards retreat, the United States has a fundamental interest in keeping the Western camp united in the face of China. However, a new Trump administration runs the risk of returning to a muddled and unpredictable policy, in stark contrast to the methodical and effective Western strategy of the Biden administration.

For the Europeans, this could mean a double ordeal: having to support the Ukrainian war effort against Russia on their own, if the United States continues to block its military assistance to Ukraine or if it adopts a policy of compromise with Putin; having to guarantee their own security, or being blackmailed by the powerful Americans who will sell their protection at the highest price.

After Brexit and the election of Trump in 2016, Europeans had begun to declare that they "must take greater responsibility for their security". And this was the impetus given to various initiatives (permanent structured cooperation on defence, the establishment of a European military planning capability, the European Defence Fund, increased cooperation on armaments). Inevitably, a possible return to power by Trump would force us to abandon the intellectual, political and strategic complacency of considering the Atlantic Alliance as the only possible option in terms of security. But a closer look needs to be taken at the conditions that might favour a change of course.

The conditions for a European alliance

It is not uncommon in history for defence leagues to be formed between countries or towns to ensure collective defence. This goes back to ancient Greece. And it is not absurd to think that the European Union, a political project from the outset, which enshrined the prospect of a common defence in the treaties more than thirty years ago, could one day move closer to this.

If the United States were to take its logic of nationalism, isolationism, strategic withdrawal and compromise with rival great powers to its logical conclusion, Europeans would face this question. After all, that is why the Brussels Treaty was signed in 1948, and it would have been useful now that the United Kingdom has left the European Union and its collective defence clause. Moreover, the current strategic context is very different from that at the start of the Cold War: Russia is a power with a GDP that lies between those of Spain and Italy, while the USSR was a superpower occupying half of the European continent and Germany was weakened and divided. It does not seem beyond the means of Europe to succeed in confronting the threat from Russia, which is already struggling to defeat the Ukrainian army.

More than financial or military resources, two political obstacles make the prospect of a truly autonomous European defence particularly complicated.

The first is the degree of political unity among Europeans. The European Union has adopted a common foreign policy and subsequently one of common security and defence. It has demonstrated extraordinary unity in its response to Russian aggression, imposing heavy sanctions on Russia and providing massive assistance to Ukraine. After the multiplication of existential crises for the European project (eurozone crisis, migratory crisis, wave of Islamist terrorism, pandemic), the latter has shown extraordinary resilience, bouncing back each time from these crises. Where does this strength come from to triumph over disunity and centrifugal tendencies? Perhaps less from a desire for federal union than from a sense of common destiny and shared values. This is indeed what is at stake in the Ukrainian crisis, where the fear inspired by Putin's aggressive despotism is combined with the defence of the values of freedom and democracy. Some even see the current crisis as a "Demosthenes’ moment"[3]  (named after the man who called on the Greeks to unite against Philip II of Macedonia), just as the European Union experienced a 'Hamiltonian moment' when it adopted the recovery plan to overcome the pandemic[4] .

Behind all this lyrical rhetoric, the reality experienced by the states must be remembered since they often have divergent reflexes and interests and are not always able to act as one. At the start of the Yugoslav crises in the 1990s, the major European powers had great difficulty in defining a united approach and imposing it, until the American hyperpower finally stepped in and managed to secure everyone's agreement. In 2003, during the invasion of Iraq, Europe was pitifully divided between a heroic but impotent Franco-German line and a majority that was complacent with the Bush Administration, in defiance of the values that the West prides itself on (peace, multilateralism and respect for the law). With Russia, the realistic approach led by Germany and France clashed with the intransigeance of the United Kingdom, Sweden and Eastern Europe, until Putin finally pushed everyone to unite against him. In regard to Kosovo, five European states still refuse to recognise the secession of this territory from Serbia and this is no doubt one of the reasons why the European Union has not taken over from NATO as it did in Bosnia. As far as China is concerned, the US had to double down on its pressure to get Europeans, lured by the Eldorado of the Chinese market and the promises of the "New Silk Roads", to harden their positions (exclusion of Huawei from the roll-out of 5G, tighter controls on foreign investment, designation of China as a "systemic rival", a strategy of "derisking" without "decoupling", etc.). And regarding Israel and Gaza, the Europeans have tragically demonstrated their divisions and, above all, their powerlessness.

Has the European Union learned from its past experiences? Could it use new mechanisms such as qualified or super-qualified majority voting to give itself the means to adopt strong, united positions? This is by no means certain. Like the rest of the world, Europe is gripped by nationalist impulses. Brexit is a flagrant illustration of this. And it is hard to see a treaty that would mean Member States giving up their autonomy on foreign policy issues (which is protected by unanimous voting) being ratified by all of them. Any common position is difficult to build because there is no natural leader: neither France, nor Germany, nor the Franco-German motor, which is no longer enough to drive all the partners. The institutions could be that leader, in a logic that is both Jeffersonian and Hamiltonian, but their legitimacy is still weak in a Union that is not a State and does not embody a "European people".

In these conditions, relying on the great American ally offers a triple advantage. The United States offers protection, a guarantee of security and the defence of democratic values in the face of hostile and rival powers such as Russia and China. They organise the relationship of strategic ascendancy in the face of divided Europeans: they have three times their defence budgets, ten times their military capabilities, and offer interoperability with the most powerful army in the world. Above all, they provide the political leadership in the Western camp. The profound meaning of the Atlantic Alliance goes far beyond defence, and General de Gaulle understood this perfectly well[5].

While France has always wanted to stir things up in this transatlantic order, as President Macron's positions show, its European partners are content with a situation that seems preferable to anarchy and to a leap into the unknown. In strategic thinking, where security must be increased and risks countered, why take the risk of calling into question what works? This is why France shifted its position in favour of reintegration into NATO's integrated command, the construction of a Europe of defence that complements NATO, a "European pillar" of NATO, without giving up the idea of pushing its partners towards greater European autonomy, which Germany and others have allowed themselves to be drawn towards in return, at least up to a certain point[6].

Obviously, if the United States were to take the initiative of withdrawing from the Alliance — which is not on the cards at the moment — the Europeans would find themselves backed into a corner and forced to consider the possibility of a genuine European alliance. But there is a second obstacle.

The Nuclear Question

Strategic and operational cooperation between foreign armies is as old as military history. The inter-allied staffs of the two world wars demonstrated this, so there is not necessarily a need for a "European army" to give birth to a "European defence". Even during the Cold War, European forces made up the bulk of allied forces. And it does not seem out of the question for Europe to put together a force capable of standing up to the Russian army and to build up a unified European command (based on the political and military structures already in place[7] ) to organise it.

The main difficulty is the nuclear issue. There are only five official nuclear powers in the world, recognised by the 1968 Nuclear Non-Proliferation Treaty — the permanent members of the UN Security Council — plus four non-recognised powers (India, Pakistan, Israel and North Korea). The challenge for states that might be threatened by a nuclear power is to seek the protection of another nuclear power. This is what the Atlantic Alliance and the Warsaw Pact were used for during the Cold War, with a complicated system of balanced deterrence. The Alliance deployed missiles, including Euromissiles, as part of a "graduated response" strategy, not ruling out the limited use of nuclear weapons to dissuade the Warsaw Pact from attacking (France had its own missiles for a tactical "last warning" strike to dissuade its adversary from attacking it). Conversely, the USSR ended up adopting the strategy of not using nuclear arms first, because it had an overwhelming superiority in conventional weapons, but this did not prevent it from developing the size of its nuclear arsenal to intimidate the West.

The war in Ukraine has brought the nuclear question back to centre stage. Putin has attacked Ukraine, whereas he has not yet attacked the Baltic states, which are members of NATO, because Ukraine is in a strategic grey zone. He took advantage of this by brandishing the nuclear threat should the West intervene in the conflict. Even if the Western countries were able to rally the G20 countries at the Bali and New Delhi summits to warn that "the use or threat of use of nuclear weapons is inadmissible" (a statement endorsed by Russia itself), the nuclear issue remains an essential strategic key to the war in Ukraine, with the grammar of deterrence laying down the principle of the absence of direct confrontation between nuclear weapon States on pain of an unacceptable risk of escalation. This is why the debate regarding sending allied troops to Ukraine is so sensitive.

If the Europeans were to move towards an autonomous European defence, they would have to settle the question of nuclear protection, otherwise this alliance would be of little value against Russia. Only France and the United Kingdom have nuclear weapons in Europe. Although France has decided to develop a nuclear force independent of the United States, unlike the United Kingdom, the role of French and British nuclear forces has been recognised as contributing to the Alliance's defence (Ottawa Summit, 1974). This role was asserted only once within a European framework in 1987, under the WEU platform on European security interests. Since then, and even more so since the demise of the Brussels Treaty and the WEU, this issue has only been dealt with within an Atlantic framework, as has collective defence. 

An additional difficulty has arisen since the United Kingdom has left the European Union and France is now the only nuclear weapon State in the Union, leading President Macron to propose to his partners a dialogue on the role of French nuclear weapons within a European framework[8].  Yet, paradoxically, it was with the United Kingdom alone that France stated (for the first time at the London summit in 1995): "We cannot imagine a situation in which the vital interests of one [...] could be threatened without [those] of the other also being threatened". A highly engaging statement that is open to a great deal of interpretation. In any case, from a British perspective, it can be taken as a reassertion that the nuclear deterrent would only be activated in the event of a threat to NATO.

If we were to imagine European defence without NATO, we would have to consider the contribution that could be made by the French nuclear deterrent and, why not, that of the British. This could result from unilateral declarations, or multilateral declarations, or a new treaty such as the Brussels Treaty. After Brexit Jean-Dominique Giuliani spoke of an Anglo-Franco-German Security Treaty: it could include a collective defence commitment recognising the specific role of the two European nuclear powers. As the use of nuclear deterrence is deliberately left in the mists of undefined "vital interests", so as to maximise its scope, declarations might be imagined implying the extension of these vital interests to France's European partners, even if this would certainly cause debate. Would France be prepared to die for its partners? And if it said so, would it do it?

The guarantee of deterrence, which is the ultimate case of the survival of a State, cannot be dissociated from a tangible guarantee through the deployment of military contingents that ensure the credibility of this deterrence. During the Cold War, the deployment of American and European troops, tactical nuclear weapons and Euromissiles ensured the continuity and "coupling" of European and American security. This lent credibility to the Alliance's ability to retaliate at any point without necessarily activating the nuclear stage, let alone launching strategic intercontinental nuclear strikes. Such a political-military mechanism would have to be put in place at European level, by deploying not only troops but also French and/or British tactical nuclear weapons on Europe's eastern flank, capable of delivering a "final warning" so as to lend credibility to the European defence guarantee in the face of possible aggression. Even during the Cold War, France never stationed nuclear weapons in Germany. Would it now be prepared to do so 2,000 km from its borders?

These debates are not just theoretical. They have started to emerge in Germany, a country that is legitimately concerned about the possible disappearance of the American security guarantee and which cannot acquire nuclear weapons without jeopardising the whole edifice of the nuclear non-proliferation treaty. Former foreign minister Joschka Fischer has spoken of a European nuclear deterrent, and several experts are openly discussing the possibility of French nuclear deployments in Germany on the basis of the collective defence clause in the Aachen Treaty, reviving the 1995-1996 debates on a "concerted" nuclear deterrent between the two countries[9].  However, the experts agree on this point: German leaders could be consulted before deployment, but the ultimate decision would not be shared and should be taken by the French President.

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This is a daunting debate that challenges many certainties and established frameworks. In itself, an extension of the French, or even British, nuclear guarantee to our European neighbours might seem like an additional safeguard, a second life insurance policy. But if it were to replace the American guarantee, would it be as protective? Do our European partners trust us to activate nuclear fire in the event of a Russian conventional threat, for example? Do they want to place themselves under the French strategic umbrella, giving France a kind of pre-eminence that Paris has always sought? Will France not take advantage of the situation to promote its own interests and positions? And what would happen if a president less favourable to European solidarity were to come to office, and with this, his or her hand on the nuclear button? Credible answers must be provided to create the necessary confidence. This is the point of the offer of dialogue made (a long time ago) by France, which so far has gone unanswered.
For most European countries, American tutelage is more natural, more protective, and easier to accept. They have little desire to take any initiative that might increase the risk of transatlantic decoupling. Is this a reason to do nothing? At the very least, the Europeans should start discussing it and preparing for all eventualities. Nor should they be afraid to break taboos and consider options. From foreign policy to external operations, from defence industry to collective defence, there is a common thread running through a shared future that has yet to unfold its full potential. Looking at what has been achieved, the balance sheet may appear incomplete. But what it could be one day should give us the courage to think and move forward.