That's what I thought about the threats to invade Ukraine. It was such a stupid idea that surely someone as intelligent as Putin wouldn't do it. But then he did. We can no longer assume he'll act rationally.

That doesn't mean he is going to invade, but it does mean we need to take his threat seriously.

Only once that I know of, and that was arguably a stalemate even though the USSR took part of Karelia. The Finns also learned their lesson there, and today (enormous network of bunkers, largest artillery force in Europe, F-35s on order, military reserve is 20% of the population) they are ready.

Plus, of course, they are EU members (which has a mutual defense clause) and NATO (whose Article 5 is well-known)