On the other hand, the unexpectedly unified response of the EU here may give him some pause should he decide to take the next step toward the Baltics.
I think the comparison with Poland is not apt (despite the stunning similarities in the headlines - which make this a fantastic read), because Hitler's invasion of Poland triggered a declaration of war by the Allies, which Hitler was prepared for, and whom he invaded directly afterwards. This step by Putin is more similar to the invasion of Czechoslovakia, which met little enough resistance that he was emboldened to go after Poland. The Allies did help to arm Poland in the months after Czechoslovakia fell, as we're arming and moving troops to Latvia now, but England and France continued to pursue appeasement with Hitler. And in any case, Hitler had good reason to believe he could win a war in the West without American involvement, and given his pact with Stalin. Putin's pact with China looks a lot shakier; the West's reaction to a non-alliance country's invasion is much more united; the signals don't point to the idea that Putin could win any territory against NATO. If Germany were still debating the nordstream pipeline, if Orban had gotten on his side, if the sanctions had not been as extreme, he might take that as a signal that we were able to be picked off. So I think some differences apply.
It's true that our reaction to Crimea was akin to the West's reaction to Hitler's initial occupation of the Sudetenland, so he probably assumed this would go as well as Czechoslovakia... but thankfully it looks like he's a step behind.