The invasion of Ukraine by Russia in February 2022 opened a new era in European foreign and security policy. Three key debates are happening at the same time: one is about the immediate security and operational emergency of the war in Ukraine. The second debate is about what optimal conditions to set in the coming years for European defence capabilities to grow fast enough to defend the continent. The third debate is about finding the appropriate international legal framework to negotiate the new terms of European security in the longer run. This article, in dialogue with the contributing authors to this special issue on Defence, calls for the negotiation of new multilateral treaties on European security and the defence of Europe, combining a firm pro-democracy stance, NATO and UK involvement, nuclear deterrence, as well as EU strategic, industrial and financial commitments.