The war in Ukraine reminds us what the EU is for. But even bigger challenges lie ahead

It's springtime in Brussels and the European Union has a spring in its step. Its leaders and institutions have been galvanised by the war in Ukraine. "The war has reminded us what Europe is really about," people kept telling me on a recent visit to the EU's capital. There's a popular theory that says European integration advances through crises. The truth is that sometimes it does and sometimes it doesn't. You'd have to be a starry-eyed Euro-optimist, for example, to claim that European unity was really advanced by the 2015-16 refugee crisis. But in its last two big ones, the…