The Holocaust involved multiple groups and individuals in Nazi Germany and its allied and occupied territories. Key figures included Adolf Hitler, who ultimately controlled the German government and the Nazi Party, Heinrich Himmler, head of the SS and a principal architect of the Holocaust, and his top lieutenants Reinhard Heydrich and Adolf Eichmann, who played crucial roles in organizing concentration camps and the systematic deportation and extermination of Jews. Other prominent Nazis included Hermann Goering, Joseph Goebbels, and Albert Speer, who contributed in leadership, propaganda, and war economy. The SS was primarily responsible for the execution of the "Final Solution," supported by the Gestapo, Criminal Police, and Einsatzgruppen mobile killing units. The German military (Wehrmacht) and civilian authorities also cooperated in carrying out mass murder and deportations. Beyond Germany, Nazi allies and collaborators, including Axis governments and local police forces in occupied countries, aided in the execution of Holocaust policies. Many individual perpetrators within these organizations and Nazi collaborators actively participated in atrocities, with names like Josef Mengele (medical experiments at Auschwitz) and others taking part in the network that enabled genocide. Major German industrialists and institutions also supported the Nazi war economy and exploitation of forced labor. Thus, the Holocaust was carried out by a wide-ranging network of Nazi leadership, paramilitary forces, governmental institutions, Axis allies, collaborators, and individuals across Europe.