In an interview with the Washington Examiner, Trump wondered, “People don’t realize, you know, the Civil War, if you think about it, why?”

Trump argued that President Andrew Jackson, who died 16 years prior, could’ve stopped it: “He was really angry that he saw what was happening with regard to the Civil War, he said, ‘There’s no reason for this.'”

He defended the claim on Twitter.

President Andrew Jackson, who died 16 years before the Civil War started, saw it coming and was angry. Would never have let it happen!
https://twitter.com/realdonaldtrump/status/859209801175269376

Trump later said people don’t realize “Republicans really did the thing” during the Civil War, though the end result was “questionable.”

The Hill – Trump: ‘Why was there the Civil War?’
CNBC – Trump: ‘People don’t ask that question, but why was there a Civil War?’
Toronto Star – ‘People don’t ask that question. But why was there the Civil War?’ Trump asks
Trump Twitter Archive