What does the EU common defence policy looks like today?
Every European country retains control of its own army but they are several cooperation mechanisms in place. Since 2003 the bloc has launched, under the Common Security and Defence Policy, more than 30 civilian and military operations in Europe, but also Asia and Africa.
France, Germany Belgium, Spain and Luxembourg also created Eurocorps, a military body that sets up rapid deployment to hotspots.
"Of course, the idea of security cooperation and military defence among member states isn't new," says Andrea Frontini, a Policy Analyst with the Europe Policy Center. "We all know the story of the European Community of Defence which was put forward in the mid 1950's. The idea didn't fly because of the French. However, the idea of not integrating but cooperating between armed forces has been resurfacing in the past few decades."
What is the Franco-German plan proposing?
Merkel and Hollande are propising the establishment of a European defence headquarters, a common stallite surveillance system and the sharing of logistics and military resources.
The idea is not the creation of a European army but basically more -and better- cooperation.
"What's strikes me, if you look at the concrete examples, they are actually pretty sensible," says Daniel Keohane, a senior researcher at the Center for Security Studies of ETH Zürich.
"Particularly on sharing the costs of different types of equipment such as military logistics. I've been by how pragmatic the proposals are. They're focusing on trying to get concrete resultats, rather than developping a grand vision that may never been implemented."
Could this be a first step towards an EU army?
Well, European Commission chief Jean-Claude Juncker did this week proposed a common defence force.
But Keohane doesn't think this will happen: "I really don't think this will happen in my lifetime. Indeed Frederica Mogherini, the EU's Foreign Affair chief, said a similar thing recently. I don't think any national government really wants to give up sovereignty over their arm forces. The real issue here, is that if you really want a European army you need a European super state."
Meanwhile, with many disagreements between EU member states, the topic of defence is seen by leaders as something to rally around after deadly terror attacks in France, Belgium and Germany.
Will every EU member states agree to these proposals?
It seems likely, especially because the UK, which is the process of exiting the union, had always been against further military cooperation.
There are however, questions about wether or not this could overlap with NATO.
"There are issue where I expect ereryone to agree" says Andrea Frontini.
"Better use of battle groups is in the interest of everybody because it's about spending less money. The idea of creating military headquarters for the EU might in fact be opposed by some member states, who are more reluctant on the EU developping a fully fledged military capacity on par with NATO."