It has not been said that Putin will succeed in bringing the Russian-occupied areas of Ukraine under permanent control with his annexation plan.

But he has already achieved one thing: he has dealt a blow to Western strategy.

It was developed by the White House and has determined the actions of the NATO countries since the beginning of the conflict.

Biden wanted to limit the war to Ukraine.

He issued a public guarantee of survival for Putin's regime and made sure that Ukraine was not given weapons with which to reach Russian territory.

For this very reason, his government recently turned down a request from Kyiv for short-range ballistic missiles.

That was a bit of a Cold War approach: you duel (indirectly) on the territory of third countries, but keep a careful eye on each other's borders.

Putin played along with this game for seven months, not even reacting to individual attacks on Crimea or in western Russia.

So the West became bolder and supplied the Ukrainians with more powerful weapons, which, as is well known, had some success.

Putin is using Biden's strategy against him

But by now pushing Russia's borders westward, Putin is using Biden's strategy against him.

The West and the government in Kyiv that depends on it would have to accept the annexations not de jure but de facto if their strategy were to be maintained.

If you give up on them, as it currently looks like, then the level of escalation has been reached that Biden wanted to avoid: (redrawn) Russian borders will be violated.

Part of Putin's trait is that he has greatly upped the ante at this level with his nuclear threats.

You have to take that very seriously, and not just because nuclear weapons always have to be taken very seriously.

Putin has his back against the wall.

His move is clever, but it's also made out of desperation.

He has come under severe military, economic and political pressure.

He tries to save his thoughtless invasion and thus his survival.

And not only politically: if he fails, he will not be able to retire at a dacha.

No one knows what Putin really thinks about the use of nuclear weapons, although they have played an increasing role in his rhetoric and politics over the years.

From his point of view, a cost-benefit analysis could look like this: A nuclear attack on NATO harbors the danger of a nuclear escalation in which Russia itself could perish.

He will want to avoid that.

The situation is different in Ukraine.

This cannot take nuclear retaliation.

Large arsenal of tactical nuclear weapons

The Russian military has a large arsenal of smaller, so-called tactical nuclear weapons that are suitable for the battlefield.

It has apparently dealt extensively with their involvement in warfare, even if it is unclear to what extent the willingness to use them offensively goes.

Several scenarios are conceivable: an operation against Ukrainian troops in the contested areas, one against targets somewhere else in Ukraine, including civilian ones, or a more symbolic detonation, for example over the Black Sea.

A deployment in the contested areas would offer military advantages against the advancing Ukrainians, but would hit new "Russian" territory.

Putin would have a hard time justifying that at home.

Therefore the other variants seem more probable,

Recognizing the danger, Washington is now trying to increase Putin's potential costs.

The White House has warned Moscow of serious consequences through direct channels.

Apparently, a conventional counterattack against Russian troops in Ukraine is under discussion.

That, too, is coolly calculated: it would confront Putin with the decision to go to war with the United States and NATO.

He rightly fears that.

It would, however, be a situation for which there is no precedent in modern world history.

In Germany, in the supposed protection of Biden's strategy, an often astonishingly frivolous debate about the delivery of battle tanks has once again been carried out in recent weeks.

Now more than ever, one should not expect America to take the blame for the allies going it alone.

No president will leave his nation's (nuclear) fate in the hands of Europeans.

The risk has increased for everyone involved, but it is primarily the Ukrainians who bear it.

The West can continue to help them best, not just with weapons, but also with unity.