I wanted to add that I think you've put your finger on it. It's not the taking. It's the keeping. I think one should take a look at not only what Russia has done, but what Russia hasn't done over the last decade.
Briefly, if you start in Georgia, Russia could have taken Tbilisi. It was ready to do so. The tanks were there, but it parked its tanks 30 kilometres away for a few days just to make the point and then it drove them home.
Similarly, in eastern Ukraine, Russia could occupy the Donbass in four hours. We won't speak of Crimea. It's worth noting that the separatists in eastern Ukraine were asking Moscow for the same annexation that Crimea had had and Putin turned them down.
Similarly, it was Putin who said that we could take Kiev in two weeks, and I think that's probably true, and it's no secret. You mentioned the speed bump; despite our troops there the Russians could overwhelm the Baltic states very quickly, but they don't because the taking is relatively easy. It's the keeping. It's the cost. It's the consequences. They're obviously enormous.
It was a Lithuanian president not too long ago who said that it wasn't a question of whether we take article 5 of NATO's Washington treaty seriously. It's a question of whether Putin takes article 5 seriously, and he does, and he'd be a madman not to.