With the Brexit deadline fast approaching, there's a growing belief that the U.K.'s exit from the EU could galvanize calls for a European army.
President Emmanuel Macron made headlines in early November 2018 when he called for a "true European Army," reigniting the debate around the EU's role in European defense and security.
However, there are still plenty of factors that stand between Brussels and a truly integrated army.
There is no consensus on what constitutes a European army. It remains ambiguous whether it would be a centralized institution operating like traditional armed forces, or a looser integration of European military personnel.
Yet for Elisabeth Braw, the director of the modern deterrence program and associate fellow at RUSI, a European army would require an unimaginable shift in the EU's governing structure.
"For a European army to happen it would have to have one centralized command," she explained. "If you think of a national armed forces, they have a government that decides when to deploy armed forces. A European army would require the same thing, it would need a European government that could decide on its own and I just think that this is extremely unlikely."
European nations would have to forego an unprecedented level of autonomy, something which they have rejected once before. In the 1950s, the French attempted to establish the European Defense Committee and create a pan-European defense force. The proposal was supranational in nature, involving common institutions, budget and military equipment.
"Unsurprisingly the French Parliament decided they wouldn't stand for that and they voted it down," explained Anand Menon, associate fellow at U.K. think tank Chatham House.
"It would have involved having a defense budget as part of the European Union which came under the European Union's budget. Now no member state is going to accept that."
Given the current period of anti-EU sentiment from Poland to Italy, it's difficult to imagine a new proposal concluding any differently.
Before the Brexit referendum, European Commission President Jean-Claude Juncker suggested that only a European army could "convey to Russia that we are serious about defending the values of the European Union." And in the wake of Russia's annexation of Crimea, the EU echoed this sentiment, revealing plans to spend just under 20 billion euros ($22.8 billion) on defense over the next seven years. While this may sound like a robust response by the EU to Russian aggression, for context, the U.K. defense budget for 2016/2017 alone was £35.3 billion ($45.8 billion).
Short of the creation of a European government, the EU would likely find it difficult to convince member states to fund a European army, particularly once it's joint largest military spender leaves the bloc. Put differently, the Commission would face similar contribution issues that have plagued NATO in recent decades.
As of 2014, NATO members are officially required to spend 2 percent of their gross domestic product (GDP) on defense. But 2018 estimates have only five nations meeting this target. While this arbitrary percentage of defense spending may not be a good metric to assess defense capabilities, it reveals just how difficult it is to attain funding requirements without control over the fiscal policies of member states.
Like NATO, the EU can ask members to fund its initiatives but it can't force them to do anything. With most EU members also being members of NATO, a European Army may find it difficult to attain enough funding to justify its existence, especially if states are considering their defense spending alongside NATO's security contributions. Speaking to CNBC at the World Economic Forum in Davos, Switzerland, NATO Secretary General Jens Stoltenberg made this idea particularly clear.
"We welcome EU efforts on defense but not as an alternative to NATO," he explained. "After Brexit, 80 percent of NATO's defense expenditure will come from non-EU allies. There is no way that EU can replace NATO."
When it comes to European security, "thinking big" it not exactly what Europe needs. As Braw highlights "NATO's role is to defend the security or territorial integrity of Europe, so it's unclear what Macron is suggesting that NATO is not already offering."
The collective defense assurances of NATO already ensure Europe's strategic security, it's Europe's tactical capabilities that require maintenance.
"Look at what the U.K. is doing with several other counties in something called the JEF (The U.K. Joint Expeditionary Force)," she said.
"It's much less ambitious than a European army but they are actually already doing it. It's a giant expeditionary force where nine countries already work together and can deploy to wherever these countries deem it to be necessary."
Large military institutions are often slow and cumbersome in response to military emergencies. It's the success of these smaller, agile initiatives that may dampen the dreams of an EU army because they actually fill capability gaps that are lacking within NATO. Partially integrating a country's armed forces with a few close allies can be an effective way to maximize defense capabilities without having to rebuild their army or undergo a costly process of standardizing weaponry.
"I think we will see more of these modest initiatives, modest but successful and that will show that actually, you can do a whole lot without starting from the top and saying you want a European army," Braw added.
Post-Brexit, the U.K and France will remain the largest military powers in Europe meaning that integration and close cooperation between the U.K. and its European allies will remain in the best interests of Europe.
Talk of a European army may not be going away anytime soon, but that may be down to its utility as a bargaining position, rather than as a serious proposal.
"The phrase European army is needless empty rhetoric," Menon told CNBC.
"No one is thinking in practical terms about a European army. They use it as a shorthand in the same way that they use the term political union, it's sort of an aspirational way that they tend to like. I wonder if it's always been the case that this kind of aspirational language has actually scared people off."
While there are certainly those within Europe who genuinely support the idea, by pushing for such a large military institution the EU is able to raise issues surrounding European defense and then possibly settle for increased integration and harmonization between forces. One could say that the idea of a European army is actually more "art of the deal" than it is "the art of war."