I am second a second generation American.
My grandparents were all born in Europe. My paternal grandparents were Polish. The Nazis murdered many of my ancestors. (About 30 that I know about) my grandparents immigrated (escaped) to America after war broke out in Europe. My grandfathers both joined the Unites States Military shortly after arriving in America.
What frankvan mentions is indeed correct. The Polish Corridor did give Hitler his “reason” for invading Poland.
What Hitler wanted to do was quite different though. He wanted to exterminate the Polish people. The Polish language was outlawed. He wanted to erase the Polish culture from the earth.
Hundreds of Polish community leaders, mayors, local officials, priests, teachers, lawyers, judges, senators, and doctors were executed in public. Much of the rest of the so-called Intelligentsia, the Polish leading class, was sent to concentration camps where they later died.
On August 22, 1939, a few days before the official start of World War II, Hitler authorized his commanders, with these infamous words, to kill "without pity or mercy, all men, women, and children of Polish descent or language. Only in this way can we obtain the living space [lebensraum] we need".
Heinrich Himmler echoed Hitler's decree:
"All Poles will disappear from the world.... It is essential that the great German people should consider it as its major task to destroy all Poles."
Hitler simply wanted Poland’s land to expand Germany.
How Could 5,000,000 Be Killed and Forgotten? 
