Apologies if there are some dead ends and rough edges in this topic, it's been split partially and some things couldn't very appropriately be placed. Please continue here about why Hitler attacked Poland...
Indeed, Roel, We have been splitting hitler´s head to find out the reasons and now - you split our efforts. What was Poland before WW2? A country much greater than its strength. Placed between two strongest powers on the Continent. A dream come true: since the end of 18th century there was no Poland. We have just found out that the main reasons why Hitler attacked it were psychological. Plus his certainty about impunity again. He was incredibly deluded, already in 1939. Anaware that in March 1939 he crossed the Rubikon. From then on, he would be treated like a rabid dog - certainly he has deserved the reputation. He was just unaware of it. His faithful Ribbentropp was too stupid to find out.
So you disagree with the split... Can't help that. It seems to me that the fact that Poland was split in the 18th century points out very clearly that even before that time the country was too large for its strength. It was an area of 'low political pressure' being flanked by expansionist nations, young and eager, like Prussia. Oddly it was Poland's fate again to be absorbed by the two new powers of the area. Ironic, isn't it?
The Poles have been experimenting a lot with their political system before the partitions. They had f. ex. an eligible king - a kind of president for life, without the right to put his heir on the throne. All nobles (10% of the population) chose parliament which had rights to make laws and new taxes.... The Jewish population had their parallel institutions, including their own parliament and judiciary. Poland was a good choice for the Jews for many centuries. This is the reason why it was the absolute center of Jewish life, just like the USA is today (besides Israel). The problem is that the country by the 18th century had no more strength to allow such experimenting. All the neighbors were centralized and militarized. But just a century earlier - it was a powerful state. Remember Sobieski´s victory at Viena? In 1939 Poland was still relatively backward vs. the neighbors, due to many factors. And no matter how large or little it would have been - it was not viable in this neighborhood.
Having an eligible king seemed to have been a bad choice in past centuries. Two examples of this are Poland(where the king was chosen)n and theGermanic empire(where the emperor was chosen). Both were handicaped vis à vis their neighbours with hereditary monarchies. The germanic empire kept loosing territories to France for centuries, and Poland was eventually split up between Russia, Prussia and Austria(all hereditary monarchies). The reason for this is most probably that in countries were the king gets chosen, the noblemen that choose him will always look for a king that is not too powerfull, and respects their rights and liberties, whereas in an hereditary monarchy centralization takes place much more easily, thus making the country more efficient. As for Poland in 1939, a weak point was that large parts of it's population were not ethnic poles, but german and ukrainian minorities, which of course sooner or later became interesting for Germany and the USSR.
Of course, particularly in the age of absolute monarchies. Morover, in Poland you had a large difference between the real aristocrats (possessing huge castles and thousands of km2 land, like the Radziwills, Potockis, Czartoryskis) and small, impoverished noblemen who sold their votes to the rich. It was a constant battle between the rich, with powerful foreign lobbies in the culisses. As to 1939-Poland, it was more its industrial backwardness (due to the fact that all former three provinces had been near the borders of the respective empires - which meant few investments and neglected, different infrastructure in each of them: try to put three parts of different countries together and see how quickly they´ll grow into one). The minority problem was not so acute, I think. The Poles dominated, of course but the minority problem was not so important as the Ukrainians and White Russians (and Lithuanians) want to see it now. My Mother´s family had a chance to observe it first hand: they lived in Lvov and ses environs. Lvov was half Polish half Jewish and the countryside - mostly Ruthenian with some Polish, Jewish and German villages. Quiet. Many say today that Poland was facistoid then. Nobody, maybe with an exception of some more extreme political parties saw it this way, then. Yes, there were some "inconveniencies" for the Jews. Like "numerus clausus" at the universities, in the later 30s. But who cared? Many Jews had money and were sending their offspring abroad to study, anyway. The "numerus clausus" limited the Jewish quota at the universities to 10% - exactly the percentage of the Jewish population in Poland. Many saw it as unjust. But how can one judge the American "affirmative policies" then? Yes, there was emigration. Both Polish and Jewish, because of poverty, not because of persecutions. Sorry for the long entry.