This was the Sarmatism theory that the Szlachta were special descendants of Sarmatians This happened 4 centuries before the Nazi's took up the idea.
The Jewish alliance with the Szlachta remained constant.
WW2 drove hundreds of thousands of Orthodox Slavic peoples who identified as part of the Russian world off of lands they had been inhabiting for 1000 years, beginning with the original Russian nation state of Kievan Rus'. Understanding the historical backdrop to this, going back hundreds of years, is critical to understanding what is happening today in the region, especially to understanding relations between Poland, Ukraine, Belarus, and Russia.
Galicia was part of Kievan Rus' dating back to the year 1,000.
For almost 700 years it was under the control of Poland or Austro-Hungry.