The present study considers whether the Russian invasion of Ukraine constitutes an opportunity for EU policy centralisation and polity-building in non-military domains, according to a social security logic. It argues that the war and growing concerns about energy security and prices have presented EU policymakers with a transboundary policy puzzle on how to ensure autonomy in energy supply, fight climate change and protect household disposable income. Then, it examines public preferences on energy and social policy options, evaluating whether the war contributed to increasing demand for supra-national capacity building and investigating the priorities (and divides) across and within EU countries in these policy areas. The findings show that social security concerns related to the war in Ukraine have been translated into greater support for policy centralisation, but they have not helped to overcome divides over conflicting policy goals, leaving policymakers with some difficult decisions.