Polish Silesia was among the first regions invaded during Germany's 1939 attack on Poland. One of the claimed goals of Nazi occupation, particularly in Upper Silesia, was the extermination of those whom Nazis viewed as subhuman, namely Jews and ethnic Poles. The Polish and Jewish population of the then Polish part of Silesia was subjected to genocide involving ethnic cleansing and mass murder, while Germans were settled in pursuit of "Lebensraum". Two thousand Polish intellectuals, politicians, and businessmen were murdered in the "Intelligenzaktion Schlesien" in 1940 as part of a Poland-wide Germanization program. Silesia also housed one of the two main wartime centers where medical experiments were conducted on kidnapped Polish children by Nazis.