The North Atlantic Treaty Organisation (Nato) retired to its sickbed as soon as Donald Trump won the presidential election last November. It finally died last Friday in the White House, when Mr Trump and Vice-President JD Vance launched a vicious attack on Ukrainian President Volodymyr Zelensky before the massed cameras of the American media.
Mr Vance, who began the assault, never conceals his contempt for Ukraine. As he said in 2022, "I don't really care what happens to Ukraine one way or the other." But the attack seemed scripted, and Mr Trump joined in right away; there are grounds to suspect that it was a pre-planned ambush.
At any rate, the confrontation ended with Mr Zelensky and his team being told to leave the White House, and the sound of doors being metaphorically slammed shut resounded all across Europe. In fact, the doors had already been closing quietly for some time, as various Western leaders concluded that the US is no longer really an ally.
As Germany's freshly elected Chancellor, Friedrich Merz, put it, one of his chief goals is to "strengthen Europe as quickly as possible, so that we achieve independence from the US". He has realised that Mr Trump is probably closer to Russian dictator Vladimir Putin than he is to the leader of any Nato country in Europe. Or to Canada either, for that matter.
Most of those leaders were in London on Sunday to welcome Mr Zelensky back from his ordeal in Washington, and even King Charles III came out to greet The Man Who Stood Up To Trump. It was an unscheduled summit with no Americans present, and the real topic was whether Europe could be defended from Russia without American support.
Of course it can, at least in principle. The population of the European Nato countries (not counting the United States, Canada or Turkey) is 480 million; Russia has only 144 million people. Nato Europe's GDP is US$21 trillion, compared to only $2 trillion for Russia. That should be enough.
Nato military forces in Europe outnumber Russian forces about two-to-one. The three million Nato troops in Europe serve in 29 different armies, so they may be less effective per person than 1.5 million Russian troops concentrated in a single army, but on the other hand, most of the Russians are fully employed trying to conquer Ukraine.
What will be harder for ex-Nato European countries to replace is the American nuclear deterrent. France and the United Kingdom have a couple of hundred nuclear warheads each, but they are under exclusive national control.
If the European Nato countries have really decided to build a new alliance that doesn't rely on the whims of a pro-Moscow US administration, they will have to figure out how to extend those modest British and French nuclear forces to protect all the Nato countries of Europe. Astonishingly, they seem ready to give it a try.
"We have a shield and [the non-nuclear Nato countries] don't," said French President Emmanuel Macron on Saturday, "and they can no longer depend on the American nuclear deterrent. We need a strategic dialogue with those who don't have it," Mr Macron told Le Parisien on Saturday.
Germany's Friedrich Merz agrees, and Mr Macron adds that he is ready to build an "autonomous European [nuclear] defence independent of Nato", although he reckons that it will take five to ten years to complete.
This is a momentous event: an entire continent is taking its leave from an alliance that has lasted for eight decades, although its ghost may be around for some time. Mr Trump and his acolytes may be gone in four years (or not, as the case may be), but it's very unlikely that Humpty Dumpty can be put back together again.
The war in Ukraine will continue, at least for a while, because Mr Putin wants to keep all the territory he has conquered and probably some more besides. There will be no cease-fire or Nato "peacekeepers" in Ukraine; the Russians think they are on a winning streak. And although nobody loved the old world order, we'll miss it now that it's gone. It was at least orderly. The next phase won't be.