President Trump yet again finds himself in possible Pinocchio land, this time for suggesting that Andrew Jackson could have — or would have — averted the Civil War. This claim is more complicated than the size of the crowd at Trump’s inauguration, however. Trump has touched a controversy that has engaged historians and the public for more than a century.

Trump’s view on Jackson is unlikely but not absurd. Jackson famously faced down his vice president, John C. Calhoun, on the possibility of states rebelling against the federal government after Congress passed a tariff that hurt the Southern plantation economy. Jackson got Congress to authorize him to use military force following South Carolina’s attempt to “nullify” the tariff, but the crisis was averted when Congress passed a compromise tariff in 1833.

Still, Trump’s comment about Jackson was in the service of his wider discussion of the Civil War. “People don’t ask that question,” he said in an interview with the Washington Examiner, “but why was there the Civil War?”

(Adriana Usero/The Washington Post)

This is truly an important question, and we can only wonder what the president would have said had his interviewer asked, “What do you think?” All too many Americans reply vaguely, “states’ rights,” even though Southern leaders, as they left the Union, made it clear that they opposed states’ rights and even named the states and rights that offended them. Americans are vague because their textbooks are vague; publishers don’t want to offend white school boards in Dixie.

[Why do people believe myths about the Confederacy? Because our textbooks and monuments are wrong.]

Trump’s conclusion about Jackson places him in a camp of 1930s historians who called it a “needless war,” in the words of James G. Randall, brought about by a “blundering generation.” That view is a product of its time, and that time is now known as the Nadir of Race Relations. The Nadir began at the end of 1890 and began to ease around 1940. It was marked by lynchings, the eugenics movement and the spread of sundown towns across the North. Neo-Confederates put up triumphant Confederate monuments from Helena, Mont., to Key West, Fla., obfuscating why the Southern states seceded. They claimed it was about tariffs or states’ rights — anything but slavery.

Earlier, everyone knew better. In 1858, William Seward, a Republican senator from New York, gave a famous speech titled “The Irrepressible Conflict,” referring to the struggle between “slave labor” and “voluntary labor.” When Mississippi seceded, it emphasized the same point: “Our position is thoroughly identified with the institution of slavery — the greatest material interest of the world.”

Simply to recognize this material interest renders improbable the “needless war” notion. Mississippi was right: Slavery was the greatest material interest in the United States, if not the world. Slaves made up an investment greater than all manufacturing companies and railroads in the nation. Never has an elite given up such a stake voluntarily. The North went to war to hold the nation together, not to emancipate anyone. But the Civil War did end slavery. When might that have happened otherwise?

Today, when slavery has no state sanction anywhere, it seems obvious that the institution could not have survived to the 21st century. But if the South had prevailed, cotton would have resumed its role as “the largest and most important portions of the commerce of the earth,” to quote Mississippi’s secession document. The Confederacy might have replaced France as the colonial ruler in Mexico and Spain in Cuba. Eyeing such a strong economic and military model, Brazil might never have abandoned slavery.

There is one more layer on this onion: The South did not quite secede for slavery, but for slavery as the mechanism to ensure white supremacy. On many occasions, its leaders made this clear. Trying to persuade fellow Texans to secede, John Marshall wrote in his Austin State Gazette in 1861: “It is essential to the honor and safety of every poor white man to keep the negro in his present state of subordination and discipline.” In 1863, William Thompson, founder of the Savannah Morning News, proposed a new, mostly white national flag for the Confederacy: “As a people, we are fighting to maintain the Heaven-ordained supremacy of the white man over the inferior or colored race; a white flag would thus be emblematical of our cause.” The government agreed and adopted his flag. Late in the war, trying to persuade Confederates to persevere, the Richmond Daily Enquirer asked, “What are we fighting for? We are fighting for the idea of race.”

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Some Trump partisans are clearly still fighting for that idea. Unfortunately, the Civil War settled only the issue of slavery — not white supremacy. Getting the Civil War wrong was part of the program of white supremacy during the Nadir. Today, getting it right is not just Trump’s responsibility — it’s all of ours.