Why did Germany's invasion of Poland make Nazi policies toward Jews more urgent?

The German invasion of Poland on September 1, 1939, made Nazi policies toward Jews significantly more urgent because it brought more than two million additional Jews under German control, drastically expanding the scale of the so-called "Jewish question".1

Prior to this, the Nazi regime had attempted to force Jewish emigration to rid Germany of its Jewish population. However, as Germany expanded its territory, it continuously acquired regions with large Jewish communities, rendering previous emigration strategies insufficient. Following the invasion of Poland, the Nazis initially utilized ghettos as temporary holding pens while they considered impractical mass deportation schemes, such as relocating Jews to Madagascar.1

Furthermore, the invasion facilitated the deployment of Einsatzgruppen—mobile killing units—which were tasked with identifying and executing individuals deemed threats to German control, including Polish Jews. This systematic use of mass murder in Poland established a lethal precedent that the Nazis later expanded during the invasion of the Soviet Union in 1941.2