Richard N. Haass is the president of the Council on Foreign Relations and the author, most recently, of “Foreign Policy Begins at Home: The Case for Putting America’s House in Order.”

THE United States is currently enjoying an unprecedented respite in the foreign policy arena — a temporary relief from the normal rigors of history that allows us to take stock at home and abroad.

It may seem outlandish to claim that we’re in the midst of a lull, given that America faces a civil war in Syria, an Iran that seems to be seeking nuclear weapons, an irresponsible North Korea that already possesses them, continuing threats from terrorists, a rising China and rapid climate change.

Yet the United States enjoys a respite all the same. For the three and a half centuries of the modern international era, great powers have almost always confronted rivals determined to defeat them and replace the global order they worked to bring about. In the last century, this process unfolded three times. The results were violent, costly and dangerous, and included two world wars and a cold war....