Britain and the United States are joined at the hip. Our intelligence agencies have an extraordinary relationship. Our foreign policies are in step around the world.
Perhaps those points - so often cited by officials in Washington and London - were never the whole story.
They certainly aren't true this morning. Not after that Commons vote and the British withdrawal of military support for any Syrian operation.
This is a stunning reversal for the special relationship and David Cameron knows it.
One thing is for sure. Ed Miliband would be wise to stay out of this town for a while. He'll be given the cold shoulder by the Obama White House if he comes calling.
The operational question now becomes: Will America go it alone?
The answer is yes. Emphatically yes.
The White House is deeply disappointed by the British vote - "discouraged" is the word being used overnight - but it doesn't change the US strategic calculation.
America will attack Syria because presidential credibility is on the line. If a massive use of chemical weapons doesn't bring a US response despite Obama's warning of a year ago, then Iran will draw the obvious conclusion with regard to its nuclear programme.
And if rogue regimes and militant groups smell American weakness, then the 21st Century could become very dangerous.
So the US will strike. But that's not to say it will be easy. President Obama hasn't just got a British problem.
He also has a Congressional problem (many in the House and Senate are demanding better consultation); a public opinion problem (Americans don't support intervention); and a timing problem (the G20 summit is in Russia next week, of all places).
So this will be a critical week for the reluctant warrior in the Oval Office.
He may be dismayed by events in London. He may be challenged by a war-weary American public.
But Obama will act anyway. Because he judges that inaction is far, far more dangerous.