“Hey, John, what’s this all about? What’s this a tour of?” Mr Trump reportedly asked John Kelly, his then-chief of staff, when they took a private tour in 2017 of the USS Arizona Memorial, a ship commemorating the surprise Japanese attack on Pearl Harbor during the Second World War.

“Trump had heard the phrase ‘Pearl Harbor’ and appeared to understand that he was visiting the scene of a historic battle, but he did not seem to know much else,” write the authors, who quote a former White House adviser concluding the US president was “dangerously uninformed”.

Presidents are not actually superhuman. They don’t actually know everything about the world. They typically know about as much as any other reasonably-well-educated American, plus maybe some extra stuff from their background. Donald Trump worked in real estate and branding. Harry Truman was a haberdasher. Andrew Jackson was a soldier.

They try really hard to give the impression that they’re super-familiar with everything – that’s part of the campaign. But…they aren’t.

And they’re gonna have blind spots, like anyone else.

What makes a President especially capable is that they have a large staff of advisors and experts under them who can advise them on things, not that they have everything in their own skull.

I know probably a fair bit about Pearl Harbor compared to the typical American. I think that there are interesting bits about it. But…to be honest, I’d say that it’s not really all that critical to be especially familiar with it as a President. If you’re a naval warfare historian, maybe a naval officer, sure.

I think that probably, a President’s important skills are being able to select competent people to work for them, being able to get along with them and willing to listen to them, being able to communicate well – since they are the public face of the US and the face of the government to the public – and maybe to conduct themselves ethically or something like that. Now…I don’t personally believe that Donald Trump ranks very well on those characteristics. I don’t think that he has the stuff that makes for a good President. But I also don’t think that having a lot of familiarity with naval battles, even an important naval battle, is that critical, either.

The Battle of Gettsyburg was also important from an American military history standpoint. Ditto for the Battle of Bunker Hill. But…I don’t really think that a familiarity with them is all that important for a President. If they need to get that information, they should know how to get ahold of it (which…it actually sounds like Trump was doing there, asked someone who should know.