“More than ever, Europe is facing huge challenges. Especially in times of crisis, our citizens must be able to recognize the value and benefits of being EU members. It is important to be able to guarantee internal security. This also implies an obligation to fight both the real threats and international Islamic terrorism in Europe”. These words are part of the Franco-German text presented on August 23 at the European Commission, in order to face the external and internal threats. A few days later, on September 11, at the eve of the Bratislava summit, another text was sent to the High Representative (HR) Federica Mogherini containing proposals to implement the Global Strategy of the European Union. The Global Strategy was presented during the first meeting without the United Kingdom, on June 28 in Brussels. After the referendum, it was clear that many balances should have been changed; however, a lot of people already speak about the Franco-German alliance, ready to take a leading role inside the European security and defense policy (ESDP). Firstly, this article will explain the content of the Lisbon Treaty’s articles which define the European common security and defense policy. Secondly, the path of the European security policy after Brexit will be presented. Finally, the objective consequences of this evolution will be analysed, in order to understand the implications of the Franco-German proposition.