Carl Bildt, former prime minister of Sweden and co-chair of the European Council on Foreign Relations, shares his perspective on European politics from the Security Forum in Warsaw, Poland.

What are the implications of the revisions to the nuclear doctrine that President Putin of Russia announced last week?

We don't really know, but I would rather see it as a sign of weakness. If President Putin had confidence in the ability of his conventional forces to achieve the aims that he has set for them in his aggression against Ukraine, he wouldn't need to do this. Does it mean that he's intending to use nuclear weapons? Not necessarily. But he wants to remind us of the fact that it's in his arsenal, and I think we know that already.