How should the European Union reform itself after the shock of Brexit? Jean-Marie Guéhenno answers the three following questions:

1. What is the problem?

2. What might a solution look like?

3. Who would need to do what?

Can the European Union (EU) be a strategic player without the United Kingdom? In 2015, Britain had the largest military budget of the European Union, followed by France and Germany. It has first-rate defense companies using cutting-edge technology. It is one of only two European powers in possession of a nuclear deterrent, and has significant force projection capacity. On the soft-power side, the UK has been one of the few European countries to meet the 0.7 percent target for official development aid. Whichever way you look at it, there is no doubt that Britain makes a considerable contribution to the strategic clout of Europe. There is also no doubt that Britain's departure and the risk of further disintegration of the EU deals a potentially devastating blow to one of the pillars of European soft power: its own example of successful integration.

At the same time, Britain as a member of the EU has made a point of limiting as much as possible the development of a European defense identity. It has prioritized NATO and bilateral cooperation with France (the Lancaster House treaties of 2010) at the expense of the EU, and has obstructed the development of the European Defense Agency. And it has not always used its own defense capacities wisely. In the Iraq war, it sided -- with disastrous results -- with the United States. In Libya it joined France to push the US into a war that eventually toppled Moammar Gadhafi, but with an end-result that is also highly problematic. So, while the UK is undoubtedly a critical component of the European strategic equation, it has rarely been a useful contributor to a European strategic posture.

And yet, the EU cannot rely only on dialogue, development aid and economic ties to ensure its security. For a while, the EU had convinced itself that soft power alone could be enough to export stability and create a peaceful and stable neighborhood. But in today's world, hard power matters. Certainly it needs to be deployed in support of a well-thought-through political strategy -- the chaos in Libya tells a cautionary tale of European countries willing to use hard power without focusing on the political aftermath. In a recent report, the International Crisis Group warned against such a narrow approach to security and stressed the importance of a political strategy built on field-based knowledge and effective diplomacy. But a political posture that is not backed by hard power is hollow. Putin's actions in Ukraine, the Islamic State's activities in the Middle East and North Africa, and the spreading instability in the Sahel, with its attendant risks of unmanageable flows of migrants into Europe should be heard as wake-up calls. Moreover, this more threatening environment is taking shape as uncertainty grows over the future of US engagement in Europe and the world at large. While Donald Trump may not become the next president of the US, his discourse reflects a changing mood among Americans, who -- just like Europeans -- are tempted to hunker down behind borders, wary of foreign engagements and focused on their own domestic challenges.

It's unclear to the West and Europe how they can make the world stable and democratic. However, they should also know that if they give up on shaping the world, the world will shape them -- and that should be of particular concern to Europe given its neighborhood. The EU will not flourish if the world fundamentally diverges from the model it has created. How, without the full participation of the UK, it can acquire the strategic clout to prevent such an evolution, is its most pressing strategic challenge.

The negative consequences of Brexit are obvious, but the EU must seize the opportunities it offers. Too often, Britain has served as a convenient excuse for the lack of progress of European institutions, including in the area of defense. UK opposition to the development of the EU's defense dimension has provided an alibi, allowing Europeans to minimize the hard security component of the "comprehensive approach" which is rightly a centerpiece of the German white paper on defense and High Representative for Foreign Affairs and Security Policy Federica Mogherini's recently-issued global strategy. NATO has been another excuse -- as if a strong NATO could exist without a strong EU. The remaining members of the EU must stop hiding behind such alibis, and demonstrate that they are getting serious about defense as a necessary complement to a broader political approach. Effectively implementing a few well-chosen projects will not address all the challenges faced by Europe, but can help create momentum and lay the foundations for a credible European strategic posture. Some should be chosen for their long-term implications, some for the shorter-term message they will send, that Europe is a provider of security and not a source of insecurity.

Among the longer-term projects, the integration of Europe's defense industry is a top priority. Governments need to stop supporting national champions, and instead back the creation of European defense companies with the resources to build genuine centers of excellence. Such consolidation will be less difficult if the European Defense Agency is empowered to play a greater role in defense procurement -- harmonizing procurement cycles, avoiding the proliferation of costly national specifications, supporting a European defense market with effective protection of strategic capacities, and managing a Europe-wide export policy.

Among the shorter-term projects, an integrated European border force, going beyond the coordination and support role of Frontex and with a coast guard component, would demonstrate to the European public that the EU can secure its external borders while keeping its internal borders open.

The EU cannot, however, limit itself to the protection of its borders. If it wants to be a serious strategic player, it should build capacities to project force beyond its borders at short notice. Such capacities will be of little use if agreement on their actual deployment cannot be reached quickly -- a case where ad hoc arrangements between willing countries are the most practical option. A smaller group of like-minded EU members should develop, in parallel, both the capacities and the decision-making institutions for effective force projection.

Such efforts within the EU should be conceived in a way that leaves the possibility, on a case-by-case basis, for the UK to participate. The best chance for the UK to eventually reconsider its decision to chart its own course outside European institutions is the development of a successful but non-antagonistic Europe. That is what convinced the UK to join in 1973, once the French veto had been lifted. The EU must keep the door open to Britain rejoining in the future, while at the same time continuing to move forward.

As the two EU nations with the strongest militaries once Britain leaves, France and Germany will have a decisive role to play in shaping the strategic posture of the EU. Other member states are watching, and their own engagement will be determined largely by German and French actions rather than by initiatives of the European institutions. But for any Franco-German initiative to succeed, France has to become more German and Germany has to become more French.

Germany may be concerned that, as the largest economy in the EU, its defense spending will inevitably overtake French defense spending if both countries spends the same percentage of their GDP -- the 2 percent goal agreed at the 2014 NATO summit. Since France has to bear the additional cost of its nuclear deterrent, the gap between German and French conventional capacities will be even wider than the gap in defense spending. But Germany should not shy away from a more proactive posture, including more frequent overseas projections of force, provided it is grounded in the rule of law.

France should embrace a pragmatic but principled posture that allows for better burden-sharing among Europeans. French policy in Africa will need to pursue its positive evolution, further distancing itself from those leaders who show little consideration for their people. An emerging European foreign and security policy combining French decisiveness and German caution could improve on national policies: It would send a cautionary message to Putin's Russia, avoid the mistakes of Libya and share the burden of stabilizing countries such as Mali or the Central African Republic.