One hundred years ago, the treaty of Versailles, the centerpiece of a set of treaties and agreements collectively known as the Paris Peace Settlements, was signed in the glittering hall of mirrors in the former home of France’s Sun King. For some, the war it brought to an end marked the final chapter of a distinct period in international relations, one dominated by a European states system that had endured since the Middle Ages and in which military conflict was relatively commonplace.

Anniversaries impose a misleading unity on a period of history. Nevertheless, it can still be useful to reflect on where we once were, what has changed, and what the prospects for the future might be. 2019 represents a moment of transition in both domestic and international politics. The backlash against globalization, the rise of intolerant and anti-democratic populisms, the tensions between rising and declining powers as well as the withdrawal of the United States from its hegemonic global role, are all calling into question norms and institutions underpinning a twentieth century world order many had taken for granted.