Hitler didn't "conquer" Austria and all Czechoslovakia though he did conquer part of it to some extent. He was handed them over on a silver platter. The Austrians themselves agreed to join Germany in the "Anschluss" and the appeasement governments of Britain, and France gave him the Sudetenland of Czechoslovakia - which happened to include all the country's fortifications. Hitler then walked in and took the rest of it to no resistance. Goebbels called these actions "the war of flowers" because of the garlands tossed into the streets as Hitler's troops marched in.
As to what I think about what happened to Poland, well I could say much, but I will say that Poland was doomed from the beginning by two things (1) the Polish corridor seperating East Prussia from the rest of Germany and (2) the topography of the land itself. Poland has been a battlefield virtually all its existence. The League of Nations, the Treaty of Versailles, and appeasement from Britain and France set Poland up for the fall. However, it is easy to sit back in these times and find fault with Britain and France. They both had lost millions, I'll say that again, millions of young men on the fields of WWI. An entire generation was lost. Three of my grandparents were Scots. All lost nearly all their male relatives of their generation. One grandmother had seven brothers - none returned from France. Having faced such losses, it can be understood by anyone of compassion how horror struck they must've been to see the spectre of such another war again.
"Do not forget your dogs of war, your big guns, which are the most-to-be respected arguments of the rights of kings."
- Frederick the Great, King of Prussia