A stable world order is a rare thing. When one does arise, it tends to come after a great convulsion that creates both the conditions and the desire for something new. It requires a stable distribution of power and broad acceptance of the rules that govern the conduct of international relations. It also needs skillful statecraft, since an order is made, not born. And no matter how ripe the starting conditions or strong the initial desire, maintaining it demands creative diplomacy, functioning institutions, and effective action to adjust it when circumstances change and buttress it when challenges come.

Eventually, inevitably, even the best-managed order comes to an end. The balance of power underpinning it becomes imbalanced. The institutions supporting it fail to adapt to new conditions. Some countries fall, and others rise, the result of changing capacities, faltering wills, and growing ambitions. Those responsible for upholding the order make mistakes both in what they choose to do and in what they choose not to do.

But if the end of every order is inevitable, the timing and the manner of its ending are not. Nor is what comes in its wake. Orders tend to expire in a prolonged deterioration rather than a sudden collapse. And just as maintaining the order depends on effective statecraft and effective action, good policy and proactive diplomacy can help determine how that deterioration unfolds and what it brings. Yet for that to happen, something else must come first: recognition that the old order is never coming back and that efforts to resurrect it will be in vain. As with any ending, acceptance must come before one can move on. 

In the search for parallels to today’s world, scholars and practitioners have looked as far afield as ancient Greece, where the rise of a new power resulted in war between Athens and Sparta, and the period after World War I, when an isolationist United States and much of Europe sat on their hands as Germany and Japan ignored agreements and invaded their neighbors. But the more illuminating parallel to the present is the Concert of Europe in the nineteenth century, the most important and successful effort to build and sustain world order until our own time. From 1815 until the outbreak of World War I a century later, the order established at the Congress of Vienna defined many international relationships and set (even if it often failed to enforce) basic rules for international conduct. It provides a model of how to collectively manage security in a multipolar world.

That order’s demise and what followed offer instructive lessons for today—and an urgent warning. Just because an order is in irreversible decline does not mean that chaos or calamity is inevitable. But if the deterioration is managed poorly, catastrophe could well follow. ...