Donald Trump said he could have done a deal to prevent the American Civil War, historian Jon Meacham has claimed.
Mr Meacham, the author of American Lion: Andrew Jackson in the White House, described Mr Trump's apparent lack of knowledge about the Civil War as a projection of the President's "fundamental and enveloping narcissism."
Mr Trump was ridiculed for suggesting the country's 7th President, Andrew Jackson, could have stopped the civil war, despite the fact he died 16 years before the conflict began.
Video not available for syndication
Donald Trump asks why the Civil War 'could not have been worked out'
“He was really angry that he saw what was happening with regard to the Civil War, he said ‘There's no reason for this,’" Mr Trump said.
“People don’t realise, you know, the Civil War, if you think about it, why,” he added. “People don’t ask that question, but why was there the Civil War? Why could that one not have been worked out?”
Asked about the comments in an interview on MSNBC's Morning Joe show, Mr Meacham said: "It's a projection of the President's fundamental and enveloping narcissism.
"He believes...he told me a year ago that he thought he could have done a deal to have averted the [civil] war."
He went on to say he and Mr Trump talked about presidents the then-candidate admired and "Jackson never came up."
President Andrew Jackson, who died 16 years before the Civil War started, saw it coming and was angry. Would never have let it happen!
— Donald J. Trump (@realDonaldTrump)
Mr Trump later tried to clarify his comments, tweeting to say Mr Jackson predicted the civil war and "was angry".
"Would never have let it happen!" he added.
Discussing Mr Trump's presidency, Mr Meacham said: "The presidency itself enhances your fundamental characteristics. It's very hard once you're there to change. Some people do, and that's why we talk about them as great presidents.
"But most people, once they're in the Oval Office, actually just become more like themselves. And I think in this case that's on a potentially tragic trajectory."