One hundred years ago, the first Department of International Politics was established at the University College of Wales, Aberystwyth, with the express purpose of seeking in Arnold Toynbee’s prophetic words (uttered many years later) – of breaking decisively with the ‘habit of nationalism’. As David Davies in the founding statement put it, by moving beyond ‘insular and vested prejudices … the shattered family of nations’ could be brought back together again and a new world order established. Yet as the history of the twentieth century showed – and the new century looks to be no nearer to realizing that original dream – nationalism has throughout continued to retain its power of mobilizing peoples and setting nation against nation. How and why this happened and with what consequences is the subject of this article.