The well-equipped German army conquered Poland in less than five weeks, despite bitter resistance from the Polish forces. On 17 September 1939, the Red Army marched into Poland as well, in accordance with the secret terms of the "Hitler-Stalin Pact". This act placed the seal on yet another division, the Republic of Poland was crushed.
The Germans fought with savage cruelty and many Poles, prisoners of war and civilians alike, were murdered by the German army, the police and SS. Einsatzgruppen and "Volksdeutscher Selbstschutz" battalions sought to bring about the "destruction of the Polish intelligentsia", one of the Nazi war aims. By the end of 1939, about 60,000 members of the Polish intelligentsia had been murdered.
While German officers criticized the murderous acts committed by the Einsatzgruppen in Poland, the German military leadership concluded that a policy of brutal repression was needed in order to accomplish the war aims defined by the Nazi leadership.