Russia’s large-scale invasion of Ukraine has ended the post-Cold War European security order, creating new realities in the countries neighbouring the EU. The war has shattered old illusions in Berlin, Paris, and other European capitals about Russia’s true intentions in the “shared neighborhood” and has underlined how much of a security threat the Kremlin’s imperialist ambitions pose for democracy in wider Europe. With its decision to grant candidate status to Ukraine and Moldova and a European perspective to Georgia, the EU has rejected the idea of a Russian sphere of influence and instead determined where its future borders should lie. But this decision has not yet led to a comprehensive strategy tailored to respond to the new geopolitical context in a region which also sees other state actors, like China and Turkey vying for influence. Below the threshold of kinetic conflict, different forms of hybrid warfare and political exploitation of socio-economic interdependencies are stress-testing the resilience of the countries in the (south)eastern neighbourhoods. An upgraded Eastern Partnership policy, which includes a new security component and supports domestic reforms and resilience as well as connectivity in the entire region still needs to be developed. In the accession process, existing formats had already reached their limits with the lack of political will and obstructionism by several member states that brought progress to a standstill. This has cost the EU a lot of credibility in the Western Balkans, but it is also closely linked to the very divisive issue of EU internal reform, which will take a long time to resolve. Combining an inter- and transdisciplinary approach to the research of the EU’s ‘control power’ in relations with malign state actors in the neighbourhood, as indeed the forces of ‘protean’ power unleashed in unforeseen circumstances, REUNIR will offer evidence-based and actionable recommendations to strengthen the EU’s foreign and security tool.