Islamic State’s coordinated attacks on Paris in November 2015 sparked a grassroots debate on security within Europe. This has reignited with every attack in Belgium, France, Germany, the United Kingdom, Sweden and Spain. At the same time, established Euro-Atlantic defence structures have been called into question by Russia’s annexation of Crimea, the United Kingdom’s unexpected decision to leave the European Union, and weakened US global leadership under Donald Trump. Europeans realise that they need to take their security into their own hands now more than ever.

The mutual defence clause of the Lisbon Treaty, Article 42.7, was triggered for the first time following the terrorist attacks in Paris in 2015. Article 42.7 has historically been largely symbolic. The solidarity was strictly political, and not clearly defined. How the member states materially reacted together under Article 42 was up to them. However, in triggering the clause for the first time, France lit the fuse on European defence.

The EU already stands rotating battlegroups of 1,500 troops ready to deploy at the bloc’s discretion. These were designed to respond to extreme and specific threats within the EU, not to function as a broad defence force. However, in late 2016, the EU expanded the scope of the battlegroups to include the possibility of military operations outside the bloc’s borders.

EU member states recognise that the threats they face demand moving past the fractured, voluntarist approach of the past and towards broad defence cooperation out from under the NATO umbrella. The discussion over the future of the defence of the European Union has now resulted in significant developments that are beginning to shift the global military architecture built after the Second World War. For the first time in decades, the EU is largely united in a desire to build new military infrastructure across Europe. However, there is not yet consensus on the scope of that military ambition.

EU defence and NATO

Free of the Soviet threat, NATO, perhaps unexpectedly, found a new role after the Cold War with military operations in Bosnia and Serbia and Kosovo. The triggering of its collective defence clause (Article 5) for the first time following the 9/11 attacks and its lead role in the subsequent war in Afghanistan further renewed the alliance. Operations to counter piracy in the Indian Ocean, enforce the no-fly zone and conduct airstrikes in Libya and strengthen air defences in southern Turkey solidified NATO’s position with regards intra-European and trans-Atlantic defence cooperation.

However, European confidence in the alliance was undermined during Trump’s first visit to NATO’s headquarters in Brussels in May 2017 when he raised concerns that not all member states are contributing enough funding and he failed to reaffirm the United States’ commitment to collective defence under the alliance. NATO suddenly looks once more like a relic of post-WWII Pax Americana – one that even the US president views as antiquated. The rise of cyber warfare, the threat of terrorism and a rapid increase in immigration are all European security concerns that the NATO military alliance appears ill equipped to counter. Deterring the threat from Russia on the EU’s eastern border may be the only task that Europeans are comfortable relying on NATO to fulfil.

Despite these reservations, any developments in EU defence integration must be undertaken with reference to NATO. The EU mutual defence clause explicitly states that ‘Commitments and cooperation in this area shall be consistent with commitments under the NATO, which, for those States which are members of it, remains the foundation of their collective defence and the forum for its implementation.’ The Berlin Plus agreement between NATO and the EU in 2002 outlined the relationship between EU and NATO assets and capabilities, and continues to be in force. Even the greatest proponent of an EU army, the French president, Emmanuel Macron, has made it clear that the autonomous EU defence force that he desires by 2020 should complement NATO rather than replace it.

NATO and the EU will thus remain co-protectors of Europe for the foreseeable future. However, this will be challenging with an isolationist in the White House who views the alliance in transactional terms and wonders if the United States is getting a good deal from the partnership. Trump has reminded the EU that the ultimate guarantor of its security must come from within Europe rather than from across the pond.

The Brexit boost

One of the most important developments that has opened the door to closer EU defence cooperation is the United Kingdom’s unexpected decision to leave the European Union by March 2019. The United Kingdom has always been the strongest opponent of integrated European defence because it sees an EU force as a threat to its sovereignty. Unlike many European countries, the United Kingdom’s robust defence technology and industrial base also gives it less incentive to be part of European defence cooperation. Indeed, the United Kingdom joined the European Union with an exception to the Maastricht treaty that excluded it from participating in EU security operations, one of the many exceptions London negotiated.

The cessation of continued vetoing of measures by the United Kingdom post-Brexit will help facilitate changes that were previously impossible. London will no longer have a say in the creation or not of an EU military force, and Brexit may end up facilitating an integrated pan-EU force for the first time in history. In a sign of things to come, EU states agreed to create a small command centre in Brussels called the Military Planning and Conduct Capacity in March 2017. This multi-national headquarters is seen as the precursor to a European army command. It was only possible because the United Kingdom removed its objections in light of its impending withdrawal from the bloc.

One caveat is that, while unenthusiastic about European defence integration, the United Kingdom has still been the largest defence contributor in the union in financial terms. As such, the defence resources of the EU will take a significant hit after the United Kingdom’s departure unless the shortfall is met by the other member states. (London has, however, expressed an interest in continuing its involvement in the few military operations that are underway that the United Kingdom is a part of.)

The future of EU defence integration

Despite Brexit and the Trump administration giving new impetus to European defence integration, it is important to note that a fully-autonomous EU army is still unlikely in the short term. Despite their political and economic union, the member states of the EU ultimately remain protective of their sovereignty – and hence their militaries. Furthermore, for such a geographically and economically united continent, European countries have surprisingly isolated defence industries. The furthest along the road the EU will likely get in the near term is a central command that integrates various militaries on a voluntary basis to behave as one ad hoc force.

This is how the various protocols for the evolution of European defence have evolved thus far, including the Synchronised Armed Forces Europe (SAFE) and Organisation for Joint Armament Cooperation (OCCAR). All of them are clearly voluntarist and bottom-up in order to incentivise states to join. The growing pains of a European military could trigger problems at a grassroots level, particularly if such a force is seen to lack democratic legitimacy. Brexit will have made the proponents of an EU military even keener to avoid an anti-establishment, pro-sovereignty backlash in the foundation stages of building an EU force.

Originally enabled in 2009 in the Lisbon Treaty, the Permanent Structured Cooperation in Defence (PESCO) initiative was signed in November 2017 by all but five EU member states. PESCO not only provides a framework for EU cooperation on defence, but actively promotes it. PESCO is a modification to Article 42 of the Treaty of the European Union through the Lisbon Treaty, which is why it is such a significant development. Fifty joint projects were already queued for discussion within a month of PESCO being signed. PESCO requires participating countries to harmonise with the European Defence Agency (EDA) before moving forward on any joint defence project. It ultimately establishes a new, permanent mechanism to build a consolidated, inter-operable and functional EU-wide military force.

Macron and the German chancellor, Angela Merkel, have both signalled a desire to move forward on common defence projects. Germany will want to be a leading – if not the leading – player in any EU force. Germany has already been moving ahead on its own, with the planned integration of one Czech and one Romanian brigade into the Bundeswehr announced in 2017. This follows the two Dutch brigades that are already integrated into the German armed forces. Germany is thus well placed to either lead a formal EU defence force or quietly sidestep the politics and lead a coalition of European militaries. Either way, the current direction of travel seems clearer now than at any point in the EU’s history.