The renewed emphasis on national political boundaries across Europe would seem to go hand-inhand with a weaker external personality for the EU. However, there are several prominent examples of EU leadership that challenge this notion, from the December 2015 UN climate change agreement to common sanctions against Russia to a new Global Strategy. This paper examines a policy area that lies at the intersection of populist outrage and external engagement: counter-terrorism. In the wake of the 2015 and 2016 Paris and Brussels terrorist attacks, the EU has made significant strides in enhancing the external dimension of its counter-terrorism policies, particularly in terms of intelligence sharing, formal and informal diplomacy, and the internalexternal nexus of security. The article argues that major terrorist attacks in 2015-2016 have served as critical junctures of crisis, driving counter-terrorism policies forward and emphasizing the notion of European boundaries beyond any functionalist or securitization explanation.The renewed emphasis on national political boundaries across Europe in the second decade of the 21 st century would seem to go hand-in-hand with a weaker external personality for the EU, as several contributions to this special issue contend (Bellamy and Kröger this issue; Zielonka this issue). However, there are many prominent examples that defy this argument. The EU emerged as the leader in marshaling an ambitious agreement at the UN climate summit in Paris, COP21 (Torney and Cross forthcoming). It has strengthened its relationship with NATO, at the same time as collectively imposing a wide-ranging sanctions regime against Russia (Cross and Karolewski 2016). And it has stood strong in the face of Brexit, even releasing a new Global Strategy and advancing plans for a defense union just days after the referendum (Tocci 2016, Cross 2016). Despite growing voices in some sectors calling for the re-assertion of national political boundaries, I argue that European political boundaries vis-à-vis the outside world are actually becoming stronger. How is the EU able to continue its march towards "ever closer Union" in its external relations while grappling with numerous challenges to integration internally?This special issue understands political boundaries as "those lines of demarcation enforced by a political authority that affect agents' range of options in producing and accessing goods widely understood to be desirable for them in the pursuit of their respective goals." EU integration has fundamentally been about a process that increasingly strengthens the notion of European boundaries over time, especially in terms of political authority, in multiple ways. To address the question of how European political boundaries are getting stronger in terms of external relations, this article focuses on the policy area of counter-terrorism. In the wake of the 2015 and 2016 Da'esh-inspired terrorist attacks in Paris and Brussels, the EU has made