What did Donald Trump do today?

He got subtweeted by the general in charge of his nuclear arsenal.

Air Force Gen. John Hyten is commander of the US Strategic Command, the branch of the nation's military apparatus that would be most directly involved in any use of nuclear weapons. Speaking at a conference in Canada today, he said he and other military leaders would not obey any "illegal" nuclear strike order Trump might issue: "We’re not stupid people."

Hyten's remarks come amid widespread and bipartisan fears that Trump is mentally unstable, and might start a nuclear war out of pique, or as a means of distracting attention from the ever-growing threat to his presidency posed by the various Russia investigations. The Senate is currently holding hearings on a bill to restrict the ability of the president to unilaterally order a nuclear attack, and members from both parties have made no secret of the fact that it is Trump specifically that they are concerned about.

Deference to civilian authority is bone-deep in United States military culture, so it is extremely rare for American military officers to raise the prospect of disobeying a president, even in a hypothetical situation where they would be legally justified in doing so. The Pentagon had no immediate comment on Hyten's remarks.

Who cares?

• It's bad if someone who repeatedly make others worry about his mental health has access to nuclear weapons.

• It's not normal for questions about whether a president would start a nuclear war to distract from a criminal investigation to be so routine.