But it is the flow of people into the European Union that has had the greatest geopolitical impact, and helped to precipitate the British vote. Stabilizing Syria and permanently curbing the refugee flow could be one of the critical factors in determining whether Europe can steady itself politically. Before the refugee crisis, the European Union was already an unwieldy and unfinished entity. Its contradictions and imperfections were exacerbated by the economic crisis. Yet it was the onset of more than a million refugees marching through Greece and the Balkans toward Germany that may ultimately prove to be the most destabilizing...