Could the world return to the 1980s?
You might think, if you listen to Vladimir Putin, or Sergei Lavrov his foreign minister, or to Jens Stoltenberg, the Nato secretary-general, that the world has suddenly shifted back in time to the early 1980s.
There is the same carefully calibrated brinkmanship (the Americans aren't quite giving Ukraine offensive weapons, but they're coming close to it), the same "Yes, you did", "No, we didn't" tone, the same not entirely phony shock and anger.
Russian aircraft regularly fly straight towards Western European airspace, and are turned away at the last instant by Nato fighters.
There is a real possibility that one or other of these Russian pilots, their transponders switched off, and deaf to the guidance of civil aviation controllers, will smash into a civilian passenger aircraft.
Why has it all blown up like this? And how dangerous could it become?
Part of the answer lies in the months immediately after the ignominious collapse of Marxism-Leninism in Russia, in the wake of the failed KGB coup against Mikhail Gorbachev in August 1991.
It was an extraordinary time. There was no government, and civil servants and senior policemen simply stayed at home. The economy, such as it was, seemed on the point of collapse.
Western political leaders were horrified. Special envoys were sent to Moscow to negotiate with the only Russian leader still standing: Boris Yeltsin.
At that stage, they would have promised him anything.
Privately, some of them seem to have told him that they would treat post-Communist Russia as a close friend and ally.
But there were other forces at work.
What President Eisenhower had once called America's "military-industrial complex" was in no mood to offer the hand of friendship to a fallen ideological enemy.
There was a lot of triumphalism about.
The US system had defeated the Soviet one, and some people were determined to rub it in.
Countries like Poland, the former Czechoslovakia, the Baltic states, Romania and Bulgaria were actively encouraged to join the Western alliance.
Nato's territory now went right up to Russia's own borders.
No US leader seemed to worry what would happen once Russia got on its feet again.
And although there was a sensation that Nato and the former Warsaw Pact, including Russia, should simply merge to become one single, huge force for peace, the US wouldn't countenance it.
There would be no equivalent of a Marshall Plan for Russia.
A year ago, vast demonstrations broke out in Ukraine, which had once been as close to Russia as Scotland is to England.
After the break-up of the Soviet Union, Ukraine had become independent, and Russia, prostrate, had let it have Eastern Ukraine and even Crimea.
The demonstrators in the streets of Kiev demanded the right to join Nato and the EU.
Eventually they forced the pro-Russian President, Viktor Yanukovych, to escape to Moscow.
President Putin saw it as a coup d'etat, encouraged by the West.
His government encouraged ethnic Russians to put on uniforms and take up weapons.
They cut off, first Crimea, and then parts of Eastern Ukraine.
It worked in Crimea last March, where the great majority of the population were ethnic Russians, and had always thought of themselves as part of Russia.
It is unthinkable now that Russia will ever hand Crimea back to Ukraine.
In Eastern Ukraine, the contest was much more violent, and turned into an all-out war. Civilians (including the entirely innocent passengers and crew of a Malaysian airliner) have died in their thousands.
The West has introduced sanctions against Russia itself, and against various named individuals, most of them close to President Putin himself. It hasn't just turned nasty, it has turned personal.
Return to Cold War?
So can there be a peaceful way out? Or are we going back to the bad old days of the early 1980s?
In Moscow last week, I was surprised to find how many of President Putin's closest supporters were worried about that.
Instead of uniting in anger against the West, they seemed genuinely troubled that things might get even worse, and that Russia's economic progress might now be destroyed.
It's always difficult to predict what President Putin will do.
But he knows what his close supporters want: they certainly wouldn't like Russia to be humiliated, but they do want a settlement.
So do most European countries. Does the US? Or does it want another triumph of the 1991 variety?
My feeling is that President Obama will decide that a rational settlement of the Ukraine problem is something he can genuinely achieve, and turn into part of his enduring legacy.
But suppose that, as I write this, one of those Russian pilots hurtling towards Nato air space miscalculates by a few millimetres?