Putin has brought war back to Europe.
He has used the customary weapons of dictators: revisionism, lies, nationalism and force.
Europe knows what they are and has had to face them in the past.
The Sudetenlanders of yesterday are the Ukrainians of today.
Europeans have learned from their history that he will not stop there, and his threats to the world on this occasion should enlighten us.
In what is likely to be a deadly spiral, the whole of Europe is at risk.
Of course the Ukrainians will respond and will not let this happen. They must be helped by all means.
Of course the most severe sanctions will be taken, quickly and unanimously, against a regime that dishonours its own people. But we also know that sanctions push those who have locked themselves into an absurd logic towards folly.
It is therefore to be feared that this will not be enough to bring reason to paranoid people who live in another world. We have known this since Munich.
Only force can stop brute force.
Europeans are now faced with one of the most difficult choices.
Putting a stop to this aggression is an imperative, dissuading the continuation of this mad enterprise is a priority, whatever the means to be used.