Polish foreign affairs minister Józef Beck in his active politics against deciding the fate of smaller countries by superpowers, was always against
partitioning Czechoslovakia using ethnic criteria, because it was (just like Poland back then) multi-national country. However - however, if such partition was to take place he demanded that Polish ethnic minority should be treated just like any other minority (German for example). It was an argument against
partitioningCzechoslovakia and not for
Taking Zaolzie (or I should rather say - taking back, after we were backstabbed by the Czechs when they took it from us when we were busy fighting on the east front) with the assent of Czechoslovakia (!), took place AFTER
the Sudetes were given back to Hitler by Great Britain and France, as a consequence
of accepting the ethnical priority by the superpowers in Munich. It was Poland's duty to protect ethnic Poles from being incorporated into the Reich.
Western propaganda was very happy to use this argument to transfer the responsibility for the fall of Czechoslovakia from their dirty hands. Beck didn't cause the collapse of Czechoslovakia - it was Chamberlain and Daladier alongside Hitler and Mussolini. Simple as that.
Generally, I have to say that looking throughout the history, Polish political, diplomatical and military conduct was extremely honourable and chivalric
towards both weaker and stronger enemies and that makes me proud, because it shows the superiority of Polish spirit and morality over those
of other European nations. That's what makes us so special and causes jelaousy, resentment and sometimes even hatred in some foreigners.
invading the country, which was ready to fight Nazis?
Czechoslovakian government, threatened by Germany, the secession of Sudets and Slovakia, left alone by France and Great Britain, was everything but ready to fight Nazis. The Czechs didn't want to fight and Hitler took what France and Great Britain gave him.