In recent years, the European Union has been bogged down by one crisis after another - from Greece to the Euro to Brexit. But happily, none of these have endangered what has underpinned European integration since the late 1940s: securing lasting peace among European states. Europe has not been spared political violence, as residents of Northern Ireland and the Basque country can attest to. But to almost all Europeans, the notion of armed conflict within their midst is no longer even thinkable. While the Catalonia crisis is not destined to degenerate into large-scale violence, European and American leaders do not appear to take the potential for conflict seriously. They are mistaken.