<P> Nazi racial policies, including the notion that people who were racially inferior had no right to live, date back to the earliest days of the party; Hitler discusses this in Mein Kampf . Somewhere around the time of the German declaration of war on the United States in December 1941, Hitler finally resolved that the Jews of Europe were to be "exterminated ." Heydrich arranged a meeting, held on 20 January 1942 at Wannsee, a suburb of Berlin . Attended by top Nazi officials, it was used to outline the plans for the "final solution to the Jewish question". Heydrich detailed how those Jews able to work would be worked to death; those unable to work would be killed outright . Heydrich calculated the number of Jews to be killed at 11 million, and told the attendees that Hitler had placed Himmler in charge of the plan . </P> <P> In June 1942, Heydrich was assassinated in Prague in an operation led by Jozef Gabčík and Jan Kubiš, members of Czechoslovakia's army - in - exile who had been trained by the British Special Operations Executive . During the two funeral services, Himmler--the chief mourner--took charge of Heydrich's two young sons, and he gave the eulogy in Berlin . On 9 June, after discussions with Himmler and Karl Hermann Frank, Hitler ordered brutal reprisals for Heydrich's death . Over 13,000 people were arrested, and the village of Lidice was razed to the ground; its male inhabitants and all adults in the village of Ležáky were murdered . At least 1,300 people were executed by firing squads . Himmler took over leadership of the RSHA and stepped up the pace of the killing of Jews in Aktion Reinhard (Operation Reinhard), named in Heydrich's honour . He ordered the Aktion Reinhard camps--the first extermination camps--to be constructed at Bełżec, Sobibór, and Treblinka . </P> <P> Initially the victims were killed with gas vans or by firing squad, but these methods proved impracticable for an operation of this scale . In August 1941, Himmler attended the shooting of 100 Jews at Minsk . Nauseated and shaken by the experience, he was concerned about the impact such actions would have on the mental health of his SS men . He decided that alternate methods of killing should be found . On his orders, by early 1942 the camp at Auschwitz had been greatly expanded, including the addition of gas chambers, where victims were killed using the pesticide Zyklon B. By the end of the war, at least 5.5 million Jews had been killed by the Nazi regime; most estimates range closer to six million . Himmler visited the camp at Sobibór in early 1943, by which time 250,000 people had been killed at that location alone . After witnessing a gassing, he gave 28 people promotions, and ordered the operation of the camp to be wound down . In a revolt that October, prisoners killed most of the guards and SS personnel, and 300 prisoners escaped . Two hundred managed to get away; some joined partisan units operating in the area . The remainder were killed . The camp was dismantled by December 1943 . </P> <P> The Nazis also targeted Romani (Gypsies) as "asocial" and "criminals". By 1935, they were confined into special camps away from ethnic Germans . In 1938, Himmler issued an order in which he said that the' Gypsy question' would be determined by "race". Himmler believed that the Romani were originally Aryan but had become a mixed race; only the "racially pure" were to be allowed to live . In 1939, Himmler ordered thousands of Gypsies to be sent to the Dachau concentration camp and by 1942, ordered all Romani sent to Auschwitz concentration camp . </P>

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