After the Brexit vote, France and Germany have put their weight behind a European Security Defence Union. This policy paper offers a cautious assessment of the Franco-German motor’s potential for a Common Security and Defence Policy (CSDP), looking into new agreements and ongoing negotiations. The drive to “revitalise” CSDP – as called for by both Defence Ministers in September 2016 – created new momentum on a range of stagnating dossiers. Though faced with an important window of opportunity, Franco-German and European constraints persist. We thus advocate an incremental approach, cementing a solid foundation for a more ambitious CSDP in the medium-term.