THEIR headquarters are separated only by a three-kilometre taxi ride across Brussels, and over the years they have declared their shared interests and common values any number of times. But despite having 22 members in common, NATO and the EU have always found it easier to talk about co-operating to than to do so. That may be about to change.

Leaders of both institutions hope that NATO’s biennial summit in Warsaw this July will mark a new era of partnership to defend Europe. NATO’s secretary-general, Jens Stoltenberg (pictured), a former prime minister of Norway, describes it as a “landmark” summit that must respond to big changes over the past two years in the threats Europe faces. Terrorists have slaughtered rock fans in Paris. Syria’s civil war has sent a wave of refugees into Europe. Russia is waging “hybrid war” in the east, achieving its aims with a mix of conventional force, political subversion and disinformation. All these problems are forcing NATO and the EU to find new ways of working together. “We have realised,” says a NATO official, “that we only own part of the tool-box.”

The EU and NATO have managed to cooperate in the past. More than a decade ago, the EU took over stabilisation missions in the Balkans that use NATO’s command headquarters and planning capabilities. These arrangements allow NATO to support EU-led operations in which the alliance as a whole is not engaged. NATO and the EU also tried to form a civil-military partnership in Afghanistan, and both have deployed naval forces to fight Somali pirates since 2008.

But the tendency has been for the two organisations to work in parallel rather than together, leading to wasteful duplication and muddle. In part this is due to the long-running row between Turkey (a member of NATO but not of the EU) and Cyprus (a member of the EU but not NATO) over the former’s occupation of the northern part of the island since 1974. Whenever possible, Cyprus thwarts attempts at cooperation. Meanwhile, America and the alliance’s more Atlanticist members, such as Britain, have always mistrusted Franco-German plans for establishing an EU military planning headquarters (and derided notions of an EU army).

However, the urgency of the new threats facing Europe may be forcing change. “We now have a real reason to work together,” says one NATO official. The hybrid warfare techniques that Russia used to annex Crimea, and to wrest control of eastern Ukraine’s Donbas region away from Kiev, require a response different from the force-on-force confrontations envisaged during the cold war. Diplomatic, communications, military and economic assets must all be used in concert. “It is a more blurred line between peace and war,” says Mr Stoltenberg. The first challenge, when faced with a hybrid threat, is to understand what is happening and to know where your vulnerabilities are. That means that NATO and the EU must share intelligence and analyse it together, and ensure that both can protect their networks from cyber-attacks. It also means protecting critical infrastructure, such as eastern Europe’s energy supply, and using joined-up communications to counter disinformation. Mr Stoltenberg is expecting three things to come out of the summit. The first will be a joint statement from him and his EU counterparts on hybrid, maritime, and cyber-security co-operation. He describes it as “an expression of will”. The second is the creation of a playbook for dealing with a range of hybrid-warfare scenarios, to speed up decision-making and answer in advance questions about who does what. The third will be linked EU-NATO exercises next year to test reactions to an emerging hybrid-warfare threat. How the two alliances will respond to the chaos enveloping Syria, Iraq and Libya is less clear. If the new national-unity government in Libya asks for it, NATO and the EU will provide help building up both military and civil institutions. The refugee crisis led to a more urgent request from Germany, Greece and Turkey for help from NATO. The alliance is working with the EU’s Frontex border agency to stem illegal trafficking and migration by means of intelligence gathering and surveillance in the Aegean Sea and at the Turkey-Syria border. A NATO official describes it as “a challenge of strategic proportions” that requires the use of armed forces. Mr Stoltenberg points to Greek and Turkish officers serving on the Aegean flotilla’s German flagship as an example of NATO-led co-operation between the EU and Turkey.

Security threats are pushing NATO and the EU to improve their relationship. But many will remain sceptical until EU politicians take the issue more seriously. Ian Kearns, director of the European Leadership Network, a think-tank, says: “There is a lot of activity at the official level, but the big challenge is political.” He questions whether the playbook idea can work; in a real crisis, sluggish EU decision-making might prevent anyone from following the script quickly enough. The “game-changer”, he says, would be a deal on Cyprus.

The Americans think more NATO-EU co-operation would be nice, but what they really want is for their allies to spend more on defence. Mr Stoltenberg agrees that it is not “sustainable” for America to cover 72% of the alliance’s spending. But he notes that European defence budgets did, at least, stop falling last year; 16 member countries actually increased them. “It is,” he says, “the first step in a long journey.”