Throughout Donald Trump’s chaotic tenure, one of the few glimmers of reassurance has been the presence at the Department of Defense of Jim Mattis. With the US Marine Corps general in position as Defense Secretary there was a chance that Trump’s wilder impulses could at least be moderated a little by a grown up.

Mattis has now resigned.

His resignation letter overnight is a devastating indictment of Trump’s policies and his treatment of America’s allies. There are none of the standard, hypocritical niceties usually employed in resignation letters. Trump is a menace is the general tenor.