According to the book A Very Stable Genius, during a private tour of the Pearl Harbor memorial, Trump asked his Chief of Staff John Kelly, “Hey, John, what’s this all about? What’s this a tour of?”

The authors explain that Trump didn’t grasp the site’s significance, as he’d “heard the phrase ‘Pearl Harbor’ and appeared to understand that he was visiting the scene of a historic battle…he did not seem to know much else.”

In a tweet the same day of his visit, Trump repeated a common misquote of Franklin Roosevelt’s description of the Pearl Harbor attack, “a date that will live in infamy.”

His wife Melania also wrongly placed the date of the Pearl Harbor attacks in a deleted tweet.

A year prior, Trump attacked Obama for not bringing up Pearl Harbor during an official visit to Japan.

The Washington Post – ‘A Very Stable Genius’ portrays Trump as erratic, ‘at times dangerously uninformed
The Washington Post – Melania Trump tweets, then quickly deletes, wrong Pearl Harbor date
Business Insider – ‘What’s this a tour of?’: Trump barely understood the significance of an iconic Pearl Harbor memorial during a private tour, new book says
The Week – Trump reportedly doesn’t know what happened at Pearl Harbor
Politico – White House misremembers historical details on Pearl Harbor Remembrance Day