European Union foreign policy chief Federica Mogherini is greeted by the head of Eurocorps, Alfredo Ramirez, right, in Strasbourg last year. | Patrick Herzog/ AFP VIA GETTY IMAGES Turf war behind EU-NATO peace deal The military alliance has a clear chain of command. The EU, however, does not.

A wide-ranging deal with NATO that aims to strengthen Europe’s military capacities is driving a power struggle in Brussels over who gets to run EU foreign policy.

The agreement, set to be signed Friday on the margins of the NATO summit in Warsaw, is a significant step forward in cooperation between the Atlantic alliance and the Union, combining NATO’s military forces with the EU’s money and ambition to fight threats, ranging from terrorism to cybersecurity, on the Continent.

EU leaders can proclaim the “Joint Declaration of EU-NATO Principals" a much-needed triumph for the bloc at a time of unprecedented crises. But even as they celebrate on the NATO stage barely two weeks after the shock of Britain’s vote to leave the EU, they will still be grappling with questions about who is in charge as the main counterpart to the military alliance’s clear chain of command.

The task is, on paper, shared between the European Council and the European Commission — what NATO diplomats like to refer to as “the other institutions in town.” But in the curiously complicated EU geometry of power, those two institutions feature three key players on foreign policy, all of whom can claim some ownership of the deal: Council President Donald Tusk, Commission President Jean-Claude Juncker and EU foreign policy chief Federica Mogherini.

Mogherini, who is a vice president of the Commission but also chairs meetings of EU foreign ministers over at the Council, is expected to join the other EU leaders and NATO Secretary-General Jens Stoltenberg for the ceremony in Warsaw but won’t herself be a signatory to the deal.

That’s spurred some resentment in Mogherini’s ranks, and among EU diplomats in general. Several ambassadors and officials involved in setting EU foreign and military policy have expressed their frustration that even though the European External Action Service (EEAS) she runs has done a lot of the preparatory work for the deal, Mogherini will not get to sign on the dotted line.

Mogherini and 3 ‘principals’

It is not only a matter of visibility or ambition — though those factors are of no small importance to Mogherini, a former Italian foreign minister with half an eye on a future political career either back in Rome or, indeed, in Brussels. One senior diplomat said there are institutional reasons for her to sign it, citing the fact that the EEAS will be the main institution in charge of implementing the deal.

Despite lobbying by Mogherini’s office to share the limelight, the joint declaration will be signed by Stoltenberg, Tusk and Juncker, known in diplomatic lingo as the three “EU-NATO Principals.” Tusk and Juncker will also represent the EU in a summit Friday morning with U.S. President Barack Obama. Mogherini will join Tusk and Juncker at the NATO summit later on Friday and on Saturday.

An EEAS official downplayed the significance of Mogherini’s supporting role, saying that “with what is going on right now it does not make any sense to create or fuel arguments.”

For some it is an issue. Mogherini’s cabinet was involved in the preparation of the agreement’s text and “there will be a clear tasking to her and the EEAS in the joint statement, making it sufficiently clear who actually ‘does the job,’” said the official, adding that it was seen as a reason for some “in favor of her cosigning.”

The official added, however, that most member countries felt the agreement should only be signed by the presidents, and Mogherini in the end did not press the issue.

“She is very careful in not declaring wars she cannot win,” a high-ranking EEAS official said.

The power struggle reflects the confusion over the leading role in EU foreign policy since Tusk took over as president of the Council in 2014. Tusk has been far more visible on the foreign policy stage than his predecessor, Herman Van Rompuy, who was more of a backroom fixer.

Tusk has visited more than 20 non-EU countries since he took office. In a report he published in May on the first 18 months of his presidency, Tusk highlighted his diplomatic efforts in the Balkans and the Middle East as part of “a record year for diplomacy.” Now approaching his third year in office, the former Polish prime minister has also tried to build up a power center of his own at the Council.

Landmark deal

Regardless of any tensions behind the scenes, the EU-NATO deal is being hailed as an important step for both the Alliance and the Union, especially as Europe confronts increasing tensions with Russia and deals with the security threats raised by the migration crisis and terrorism.

The deal is expected to be “an effective division of labor with the Europeans that will take more responsibility for their defense,” said Stefano Stefanini, a former Italian NATO ambassador, adding that the biggest NATO member and contributor also sees upsides. The “U.S. is ready to see it happening, as long as it happens.”

The agreement, according to an internal Commission briefing document obtained by POLITICO, will include measures to deal with “hybrid threats” — diplomatic jargon that mainly refers to the destabilizing effect of Russian propaganda or cyberattacks on IT infrastructure. It will also include support to non-EU, non-NATO countries in Southern and Eastern Europe to build defense and security capabilities. Importantly for the EU, it will also include cooperation on border control and naval patrols in the fight against illegal migration.

The deal has the backing of EU countries that are not in NATO, such as Sweden and Finland, because it arrives at a crucial moment. “With the conflict in Syria, terrorism and migration everybody came to realize that we need it,” said Sweden’s ambassador to NATO, Håkan Malmqvist. “We need to cooperate more in the EU and NATO context, this is just a start.”

Diplomats hope the agreement will help to overcome past difficulties the pair have had in working with each other. NATO’s military staff, for example, have been reluctant to divide labor and share information with EU institutions that have a lot less experience in military planning.

Juncker, according to the internal Commission memo, will use the summit to push for “full implementation” of an agreement that the EU and NATO reached in March on naval support in the Mediterranean — and ask for even more help. NATO military authorities, according to the memo, were “currently exploring different options in that respect.”

Expect to hear both sides repeat calls for more of a focus on defense issues in Europe — and especially for higher defence spending, a longtime NATO request to its European members.

The EU side hopes to profit from increased defense budgets too: “NATO should call Europeans to intensify efforts towards a stronger European defense,” the Commission memo reads.