To historians, it is an astonishing failure that so many Americans still cannot seem to grasp why the Civil War happened, because the answer is relatively straightforward and unambiguous. The leaders of seceding states and of the Confederacy made it entirely clear that they left the Union to protect slavery from what they believed would be its destruction by Abraham Lincoln and the Republican Party. This was no secret at the time, and it requires no particular skill in reading historical documents to reach that conclusion today. It is simply true.

And yet, no less than White House Chief of Staff John F. Kelly, in an interview with Fox News Channel host Laura Ingraham, called Confederate General Robert E. Lee an honorable man,” and stated that the Civil War resulted from “the lack of an ability to compromise” among “men and women of good faith on both sides.”

That many other Americans would surely echo Kelly’s misunderstanding of the causes of the Civil War can be explained in part by their education. This is particularly the case for older generations because, for decades, American schoolchildren learned that the war was about abstractions such as “states’ rights” or a “blundering generation” of politicians who could not sort out their differences. Considerations of precisely what rights states believed important enough to go to war for, or of precisely what differences national politicians could not resolve, were actively and purposefully avoided.

Indeed, educational elisions of these sorts remain a problem in many American schools to this day. Still, they only go so far as an explanation. It is 2017, not 1960, and John Kelly is not a stupid man. He knows — and if pressed would likely concede — that slavery was central to why the Civil War broke out. That reality, in turn, makes the question less about his miseducation and more about his and others’ insistence in talking around the cause of the war rather than actually talking about the cause of the war.

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Sometimes, of course, such obfuscation is rooted plainly in racism. As we have seen all too clearly in the last year, the overlap of neo-Confederate ideology with white nationalist ideology is extensive. Whether calculated or not, Kelly’s omission of the primacy of slavery in talking about the causes of the Civil War, complete with a deeply unfortunate reference to people of “good faith on both sides,” surely went down well with at least some substantial component of his boss’s political base.

A less cynical assessment of why many Americans continue to have trouble articulating the fundamental connection between slavery and the Civil War might point to two other reasons: an insufficiency of historical thinking; and an unwillingness to confront or to take seriously the experiences of enslaved people themselves.

Wars do not happen magically, and governments do not engage in them because of generic considerations of political ideology or because some kind of broad political process breaks down. They engage in them for specific historical reasons, and understanding those specific reasons requires grappling with the particular roots of conflicts on their own terms.

In the case of the Civil War, however, thinking historically about slavery remains difficult for many Americans. Especially among white Americans, it can be hard to imagine or accept that in the past, some of their own countrymen — and sometimes their own ancestors — were so devoted to slavery that they would court treason and death to protect it.

Arguably more problematic is that too many white Americans do not account for the historical circumstances of black people so as to consider what the Civil War meant to them. Even putting aside the fact that politicians in the United States did compromise on the issue of slavery repeatedly in the generations after independence, for John Kelly to say that the war happened because of a failure to compromise is to suggest that avoiding the war through compromise would have been preferable to fighting it.

That argument can certainly be made, and there are people who would make it. But making that argument in an intellectually honest way entails recognizing that any compromise almost certainly would have meant bondage for the indefinite future for four million people and their descendants. To make a case for the value of “compromise” in the abstract is to show a shocking indifference to that reality and to the desires of enslaved people for their own freedom.

Most Americans do understand, at least at some level, that the issue of slavery was critical to the outbreak of the Civil War. But if more people approached thinking about the Confederacy, the Civil War, and the compromises the South was interested in extracting from the Union from the perspectives of the enslaved, they would be less likely to obscure the real reasons why the war came, why perhaps it had to come, and why it was vitally important that the Confederacy lost.

Joshua D. Rothman is a professor of history and Chair of the Department of History at the University of Alabama. He is the author of several books, and is currently working on a group biography of the leading domestic slave traders in the United States.