The mood in the European Union on military affairs is undergoing a seismic shift.

Policymakers across the Continent finally agree that hard power — long viewed as antithetical to the EU's raison d'être — is now essential to the bloc's survival.

The question is how, or sometimes if, the EU's militaries should work together.

After decades of the EU viewing itself as a peace initiative and seeing defense as a matter of national sovereignty (made all the less urgent thanks to the EU's existence) there is still no consensus on how to create, organize or wield joint military power. Few are eager to turn over authority to Brussels.

Trade wars might be fought better with collective muscle, but real wars? On that, EU leaders remain divided.

The Commission has proposed a €13 billion European Defense Fund for the bloc's next long-term budget.

In Germany, under fire from U.S. President Donald Trump over military spending, there is renewed debate about becoming a nuclear power. In France, President Emmanuel Macron, citing a worrisome lack of joint EU military planning, has called for "a common intervention force, a common defense budget and a common doctrine for action."

In the U.K., security cooperation is a cornerstone of Prime Minister Theresa May's proposed post-Brexit relationship with the EU — one of few British demands that has won unvarnished praise in the rest of the EU.

And in Brussels, the Commission has proposed a €13 billion European Defense Fund for the bloc's next long-term budget, in part to expand a list of 17 joint defense initiatives approved in December by the European Council under what is known as Permanent Structured Cooperation (PESCO). The European Parliament has even called for creating a directorate general for defense in the Commission.

Existential threats

Advocates of military cooperation say no less than the EU's survival is at stake. "Only together, we are strong," Michael Gahler, a German member of the European Parliament, said in July after the approval of a €500 million fund for research and development of defense industrial products. "Only united will Europeans face the challenges that emanate from Russia, disintegrating states in the neighborhood and, unfortunately, the currently incalculable U.S. foreign and security policy."

But it remains far from certain that European capitals can find the political will, the technical capabilities, the financial resources and, most fundamentally, the mutual trust necessary to transform the EU into a military superpower capable of countering Russia, acting independently of the United States, or ultimately wielding global influence.

Nor is it clear that national governments want to relinquish control. The bloc is still wrestling with the decades-old question of how much of hard power to put under the authority of Brussels — a question further complicated by the EU treaties, which bar direct financing from the bloc's budget of weapons and military operations.

At a June meeting of top national defense officials, there was some skepticism about giving Brussels more powers, said a senior EU diplomat.

Some EU leaders, most notably Hungarian Prime Minister Viktor Orbán, have called for creating an EU army. And Commission President Jean-Claude Juncker, urging greater strategic integration, has declared that "soft power alone is not powerful enough in an increasingly militarized world."

But many others are reluctant to cede authority over national security, afraid of a backlash from voters and, in some cases, worried about undermining NATO.

"NATO is still our best guarantee of peace and security," Dutch Prime Minister Mark Rutte said in a speech earlier this year. "But that doesn’t mean that the EU can afford to do nothing."

Rutte expressed support for the European Defense Fund and for the PESCO initiative, which 25 of 28 member countries have joined. But he stopped well short of endorsing an EU army. "It begins and ends with the member states," he said.

Trying to find the balance

In a sign of how leaders are still searching for the right balance, the Netherlands was one of eight countries, along with Belgium, Britain, Denmark, Estonia, Germany, Portugal and Spain, to sign up with France on Macron's initiative to create a "common intervention force."

"What Europe ... lacks most today is a common strategic culture," Macron said in September 2017, when he first proposed the idea.

German Chancellor Angela Merkel has also sounded positive, if cautionary, notes.

While initial steps may seem small, experts say they represent a revolutionary shift after decades of inaction.

"Let’s be honest — Europe is still at the very start when it comes to a common foreign policy," Merkel said in a speech in May. "However, this is what we will need for our own survival because the nature of conflicts has changed completely since the end of the Cold War. A great many global conflicts are taking place on Europe’s doorstep. And it is not the case that the United States of America will simply protect us. Instead, Europe must take its destiny in its own hands. That is our job for the future.”

Merkel has cited the sprawling mix of weapons systems across Europe, a point also stressed by Gahler, the German MEP. "Nobody can explain why there are 178 different weapon systems in the EU compared to 30 in the U.S.," Gahler said. "The U.S. has a single type of main battle tank, while in the EU we have 17."

EU military cooperation inches forward

There is some unity among countries that joined PESCO, even if actual progress is slow.

The European Council in March approved an initial list of projects, including the creation of a European Medical Command, development of cyber rapid-response teams, and construction of an armored infantry fighting vehicle, to be built by Italy, Greece and Slovakia.

Diplomats said only two projects — the cyber initiative led by Lithuania and a Dutch-led initiative on military mobility — have made concrete progress so far.

But already defense ministers are looking at a further 33 projects put forward by member countries in recent months. They plan to draw up a shortlist for approval by December.

The Commission also allocated €500 million in 2019-20 for defense industrial research projects, which one European NATO official said would help reduce reliance on Washington. “Currently it's all based on U.S. and U.K. technology,” the official said. "Once this will be done, EU member states will be in the position to choose between U.S. and EU products.”

While these initial steps may seem small, experts say they represent a revolutionary shift after decades of inaction.

"The European Commission has found its way into the European security and defense sector," Chantal Lavallée, an expert at the Institute for European Studies, wrote in a recent paper for the Real Instituto Elcano in Spain. "To the surprise and skepticism of many, given that this sector has long been considered a domaine réservé of the member states, ambitious Commission initiatives have come to fruition."

Overcoming old divisions

Still, officials, diplomats and experts said major obstacles to greater EU defense integration remain, not least of which is a largely unspoken undercurrent of distrust reflecting the long shadow of two world wars.

And even as Trump has bludgeoned NATO allies to increase military spending, the U.S. has started expressing concerns about greater EU cooperation — saying all programs must be in close coordination with NATO, where Washington has major sway.

Some EU countries have shown a willingness to go their own way. Poland, for instance, asked the Trump administration to establish a new military base on its territory — a unilateral request that was not discussed in advance either among EU partners or NATO allies — and that some other European countries fear could unnecessarily provoke Russia.

And some European countries, mindful of Germany's role in past wars, are not as keen as Trump to see the EU's richest country meet NATO's spending target. "I’m not really sure all member states would like to see Germany spending 2 percent [of GDP]," one senior EU diplomat said.

This article is part of POLITICO's autumn 2018 policy primer.