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.