From the days of his earliest foreign policy salvos, launched from the neoconservative mothership Commentary in the 1980s, Robert Kagan has held two core beliefs. First, though it is rare in human affairs, and threatened on all sides, freedom is possible in a fallen world. Second, only the United States can provide that freedom by superintending the international system, and resorting when necessary—distressingly often, it turns out—to armed might. One principle is pleasingly universal, if melodramatic and selective about how much freedom its defenders have achieved and what the most serious threats to that freedom are. But the other principle, which Kagan presents as a necessary corollary, routinely corrupts the first with its aggrandizing nationalism and violent warmongering.

After the Iraq War, Kagan and his fellow neoconservatives earned the fury of American liberals for instigating one too many catastrophic foreign interventions on these principles. Kagan explained the mission in his Washington Post column on the very day of the September 11 attacks, calling on Congress to declare war on all enemies. “It does not have to name a country,” he suggested. (It didn’t.) Within three months of that comment, Kagan clarified that the case for invading Iraq did not require “linking Saddam directly to the Sept. 11 attack.” As the toll of the war became clear, liberals—many of whom had signed on—felt misled. Kagan’s credibility plummeted. “Why would any rational person listen to Robert Kagan?” Glenn Greenwald wondered in 2007. Kagan and his fellow neoconservatives, journalist James Fallows commented, “have earned the right not to be listened to.”

By the late 2000s, the consensus was that neoconservatism, as the writer Jacob Heilbrunn observed, “not only destroyed conservatism as a political force for years to come but also created an Iraq syndrome that tarnishes the idea of intervention for several decades.” In fact, a new left and new right demanding military restraint reemerged from the blowback, carnage, and defeat to which Americans have seen their wars lead. The isolationist right roared into prominence thanks to Donald Trump’s call to end “Endless Wars” and attempt to withdraw troops around the world. And, inspired by peace candidate Bernie Sanders, the left gained a hearing for its critiques of liberal internationalism since 1989, with figures such as Trita Parsi and Stephen Wertheim launching initiatives for a policy of restraint.

And yet in this desperate pass, Kagan—the most sophisticated spokesman for the neoconservative foreign policy school—has gotten another hearing. In the last few years, Kagan has reconstructed himself as a defender of America’s liberalism against threats within and without, and helped to reforge a centrist pact that approaches world affairs from the shimmering belief that the greatest armed power in history is the exceptional and indispensable force for global freedom. That belief had been tottering on the precipice; the Ukraine War restored its appeal overnight.

F. Scott Fitzgerald was wrong: Neoconservatives, at least, can get a second act in American life. Kagan’s new history of U.S. foreign policy in the early twentieth century, The Ghost at the Feast, shows how he has repackaged his beliefs for an era of recently challenged but suddenly renewed optimism about America’s exceptional role in world affairs. The book is a study of the years leading up to World War II—a period that both liberals and neoconservatives like to use to prove that sometimes America’s only responsible option is military intervention. Yet as Kagan proceeds through the years of rejection of U.S. warmongering before 1941, and the “great debate” about whether to intervene at all before Pearl Harbor, he inadvertently recognizes the power of the historic and recent alternatives to U.S. militarism. While he is regaining influence, his history can equally be read as cautioning against militarist lessons so often drawn from the past.