There are foreign policy questions at stake in this election that run so deep and touch on such fundamental assumptions about America’s proper place in the world that it is nearly impossible for any one question posed to the candidates not to miss the forest for the trees. That is because Donald Trump’s “America First” movement self-consciously departs from the beliefs, traditions, and practices that have defined American foreign policy since a time before nearly every living American can remember: since the administrations of Roosevelt, Truman, and Eisenhower cemented them as the bipartisan consensus in the aftermath of World War II. Indeed, “America First” borrows its very name from the movement that opposed every tenet of that consensus before the war’s start. It should be no surprise, then, that historical debates surrounding World War II, long dormant, have become hot political topics once more.

These debates are not some esoteric diversion for history buffs. Candidates’ answers to these historical questions would tell us more about their fundamental views on America’s role in world affairs than any specific question about today’s top stories ever could. For that reason, they should be part of tonight’s vice presidential debate.

Sen. J.D. Vance, the Republican vice presidential nominee, has already found himself handling one such historical hot potato. Ten days ago, he headlined Tucker Carlson’s tour event in Hershey, Pennsylvania, just weeks after Carlson ignited a firestorm by hosting on his show and endorsing an amateur historian who argued, among other things, that Winston Churchill—not Adolf Hitler—was the “chief villain” of World War II and that it was a mistake to fight a war to stop Hitler’s conquest of Europe.

Vance, of course, is not responsible for every idea Carlson promotes. But the vice presidential nominee also refused to distance himself from Carlson after that fiasco, despite the outcry that sprung up across the political spectrum. Carlson’s lobbying effort was reportedly crucial in persuading Trump to choose Vance as his running mate, and for the primary reason that Vance was the most anti-“neocon” of all the finalists for the job. This makes sense, given that “neocon” is an epithet that Carlson and Vance both regularly hurl at those who disagree with them, using the term as a synonym (in their minds at least) for “warmonger.” Indeed, the policy stance that most clearly binds Carlson and Vance and distinguishes them among Trump’s many backers is their strident anti-interventionism and 180-degree turn away from the foreign policy traditions of George W. Bush and Ronald Reagan. It is most clearly evident in—though by no means limited to—their deep and open hostility to Ukraine in its defensive war against Russia.

Vance has fashioned himself as an outspoken proponent for and a nascent intellectual leader of Trump’s often amorphous “America First” foreign policy project. And given the vagaries and inconsistencies of Trump’s own views on the subject, it matters greatly who holds the No. 2 spot in his administration. Foreign policy is clearly the area where Vance differs most from Trump’s first running mate, Mike Pence, who is a strong supporter of Ukraine and Reaganite proponent of robust American world leadership. Vance would have an outsized ability to steer foreign policy in a very different direction during a second Trump term, and even more so as a leader in the Republican Party in the years thereafter.

So what does Vance mean when he advocates “America First?” We already know that history plays a foundational role in Vance’s worldview; he has said many times that the Iraq War, which he believes was a historic mistake, anchors his entire foreign policy outlook. He has every right to take that position and argue it, not least because he personally bore the costs of that war by serving his country in it. But to lead this country, he also needs to answer the question that logically follows next: What other wars in American history does he view as mistakes? Where is the line between, as he might put it, the machinations of “neocon warmongers” and the necessary wars that America was right to fight? The Gulf War? The Korean War? Was it right to supply military aid to the Soviet Union’s enemies under Ronald Reagan? What about supplying aid to Hitler’s enemies in the 1940s? Was America also wrong to get involved in that war?

Voters deserve to know whether Vance views the policy choices made by America’s leaders in the run-up to World War II—supporting the alliance against the fascist powers by supplying military aid to Britain, China, and the Soviet Union—as mistakes. Should America have instead followed a policy of “non-intervention” and let Europe and Asia sort out their own mess, regardless of who won? That, of course, is exactly what the most famous iteration of the “America First” movement advocated. Founded in 1940, but channeling sentiments that ran strong all throughout the 1930s, the America First Committee argued that America should limit its intervention solely to the Western Hemisphere and not play any part (including the supply of aid) in conflicts that did not concern it directly—among them Hitler’s invasions of Czechoslovakia and Poland and subsequent battles with Britain and the Soviet Union. 

World War II disabused most Americans of those anti-interventionist instincts; indeed, the America First Committee dissolved itself after Pearl Harbor. American foreign policy—and the very foundations of the world order—completely changed as a result of that conflict. We still live in a world defined and maintained by the treaties, trade arrangements, alliances and American military deployments and security guarantees (above all with NATO and our Pacific allies) that were established in the years following its end. They were consciously designed by America’s leaders to prevent a replay of the 1930s: to stop aggressive dictators early on before their wars of expansion could spiral into a third world war.

It is no accident that a multitude of historians have drawn direct lines of comparison between Hitler’s expansionist wars against Germany’s neighbors (especially its first victim, Czechoslovakia) and Vladimir Putin’s expansionist war against Ukraine and threats of future wars against Russia’s other neighbors. The parallels are striking. If Vance is so vociferous in arguing that America First today means refusing to aid Ukraine in today’s conflict, does he think America First was right back in the 1930s and ‘40s as well?

If so, he needs to explain to voters why a world where America had never intervened would be a safer place today. And if not, he needs to explain to them why America First was wrong back then but right today. Vance is not the first politician to argue that America’s role as leader of the free world should have ended after our victory in the Cold War (or indeed, that it never should have fought the Cold War to begin with). It is possible that he could be right: that we are in a new age where different rules apply, and that now is the time to leave behind the lessons that we learned from World War II.

But history has a habit of punishing those who ignore its lessons and think that the fundamental nature of the world has somehow changed. Today’s Americans inherited a system of world security that was built by America’s Greatest Generation and paid for with their blood and sacrifice. That generation rejected its version of America First. The onus is on Vance to explain to this generation why we should embrace it today.