During the summer of 1941, the Nazis broke their agreement and invaded the Soviet Union. Hitler believed that Jews had created communism.The war in the East was aimed not merely at conquest but at the destruction of millions of Jews and Slavs.. By the end of the summer of 1941, the Nazi leadership had made plans for six extermination camps on Polish soil.

: https://www.theholocaustexplained.org/the-final-solution/the-death-camps/chelmno/