Phase two of the Brexit negotiations is starting and all eyes are on the future economic partnership. The other key issue – the future security partnership – is often neglected. One reason for this neglect is that stakes are lower in this policy area that is far less integrated in the context of the EU. A second reason is that there seems to be more room for compromise. In fact, both Brussels and London have indicated that while basing post-Brexit defence cooperation on existing models, they might strive for a more ambitious version. What does this mean in practice? This blog post assesses two existing and two new models for defence cooperation in light of EU and UK interests.