Among other things, he thinks a strategic defence review should include the strategic nuclear deterrent. The departure also follows a series of tense Whitehall clashes between Defence Secretary Liam Fox and Number Ten, several of which have been aired in public.
Dannatt's departure does strengthen the claim to prescience of those who worried that the announcement of his appointment - to the then Leader of the Opposition, during a pre-election year party conference - looked like a party political gimmick.
Step forward Chris Grayling, who told the BBC at the time.
I hope that this isn't a political gimmick. We've seen too many appointments in this government of external people where it's all been about Gordon Brown's PR."
He later blamed a "misunderstanding" for criticism. "I am really delighted it is a Conservative appointment – it's a bit embarrassing really," he said
While he may not have become Home Secretary after a slightly more prominent gaffe than that one. But a man who these days seems to be too seldom praised for his sure-footed political touch can surely now claim to have, albeit accidentally, called this one right.