These political and ideological linkages between America’s past, present, and future provide this book’s conceptual anchor. They ensure that a work that is principally a history of isolationism also speaks directly to where the United States’ relationship with the world may be headed. This book’s reclamation of the virtues of isolationism does not constitute an endorsement of an American retreat from the global stage. But rediscovery of isolationism’s merits—along with sober acknowledgment of its drawbacks—will help the country reclaim its most valuable tenets. Those tenets should figure prominently in the informed and searching debate that Americans need to have about the country’s future role in the world.

Engaging in that debate is an urgent priority; the United States has been living with a dangerous gap between its commitments abroad and the economic and political resources needed to sustain them. As Walter Lippmann, one of the most influential journalists of his generation, wrote in 1943, “in foreign relations, as in all other relations, a policy has been formed only when commitments and power have been brought into balance. . . . The nation must maintain its objectives and its power in equilibrium, its purposes within its means and its means equal to its purposes, its commitments related to its resources and its resources adequate to its commitments.” The United States’ purposes and its means have been out of kilter, which is why many Americans have been calling for efforts to scale back foreign commitments and restore a balance between the nation’s objectives and its economic and political resources.

Donald Trump’s isolationist pronouncements may have shocked the establishment, but they certainly resonated with an electoral base that has been struggling to make ends meet. Even before he came on the scene, opinion surveys were picking up a discernible inward turn among the public—precisely why Obama tried to rein in foreign entanglements and why Trump ran on a neo-isolationist platform. According to a 2013 Pew Research Center survey, titled “American International Engagement on the Rocks,” the U.S. electorate has been turning its back on foreign affairs. “The depth and duration of the public’s disengagement,” the report notes, “goes well beyond the periodic spikes in isolationist sentiment that have been observed over the past 50 years.” A separate poll revealed that over fifty percent of Americans believed the United States should “mind its own business internationally,” by historical standards a very high level of isolationist sentiment.

The United States needs to pull back from an excess of foreign commitments if it is to bring ends and means back into alignment—and the nation’s isolationist past provides valuable guidance for doing so. The country can and must draw lessons from the isolationist playbook to advance its interests as it seeks to restore equilibrium between its objectives and its power. An informed, cautious, and selective pullback is far preferable to a precipitous retreat—precisely what may lie in store should internationalist overreach prompt Americans to again embrace isolationist excess. Finding the middle ground between internationalist and isolationist extremes is one of America’s paramount challenges in the years ahead. The grand strategy of judicious retrenchment offered in this book’s concluding chapter seeks to arrive at that middle ground. It seeks to extract the wisdom of America’s isolationist as well as its internationalist traditions to bring purposes and means back into balance. Excavating the tension between isolationism and internationalism can help restore prudence to U.S. statecraft.

Charles A. Kupchan is Professor of International Affairs in the School of Foreign Service and Government Department at Georgetown University, and Senior Fellow at the Council on Foreign Relations. From 2014 to 2017, Kupchan served in the Obama administration as Special Assistant to the President on the National Security Council. He also served on the National Security Council during the Clinton administration. He is the author of The End of the American Era (Knopf), How Enemies Become Friends (Princeton), and No One's World (Oxford).