The Nazis regarded the Poles as non Aryans, a lower race and as such they considered them 2nd class citizens, they were to be denied education and become slaves.
In the words of Dr Robert Ley , a special adviser to Adolf Hitler
"A lower race needs less space, less nourishment and less culture than a higher race"
More than 6 million Poles died in the war but only 1/10th of those were due to the hostilities - the rest were tortured or killed by the Nazis to satisfy their ideals.
The Germans took Warsaw on 14th September 1939 just 2 weeks after the invasion of Poland started.
Germany wanted slave labour to fuel their growing war machine. Polish people were banned from Schools, colleges and Universities, Polish intellectuals were either killed or sent to labour camps. The Germans took over the local newspapers and even designated some buildings as 'Germans Only'
During the rounding up of the Jews many were shot dead in the street - to this day there are still little impromptu altars on the streets of Warsaw at the site of the shootings which list the victims names and date of their death.