Greifelt was born in Berlin in 1896, the son of a pharmacist. He joined the German army in 1914 and fought in the First World War. After the war, he retired from the army with the rank of Oberleutnant. Subsequently, he was a member of the Freikorps. During the Weimar Republic, Greifelt worked as an economist at a Berlin joint-stock company until he was laid off in 1932 due to the difficult economic situation in Germany. After the Machtergreifung, Hitler's rise to power, Greifelt joined the Nazi Party in April 1933 and the SS in June 1933. As of August 1933, Greifelt was a speaker on the Persönlicher Stab Reichsführer-SS. From early March to mid-June 1934, Greifelt was business leader for the chief of staff of SS-Oberabschnitts Mitte/Elbe, and then by mid-January 1935, chief of staff of SS-Oberabschnitt Rhein/Rhein-Westmark/Westmark. He then headed the Central Registry of the SS-Hauptamt. After the beginning of the Second World War, Greifelt was appointed Chief of Staff of RKFDV in October 1939. He was instrumental in the "planning and implementation of population relocation in the context of Generalplan Ost". In the SS, Greifelt rose quickly through the ranks, reaching Gruppenführer by 1941. He ultimately reached the rank of SS-Obergruppenführer und General der Polizei on 30 January 1944. In February 1942, whilst serving on Heinrich Himmler's staff, Greifelt wrote a directive for dealing with children. According to what this laid out the Polish government had been responsible for seizing ethnic German children and placing them in orphanages and it was the duty of the Nazis to reclaim these children. He continued that those who "looked" German should be taken from orphanages, taken for examination at the SS-Rasse- und Siedlungshauptamt before undergoing extensive psychological study. Those that were found to be of desirable racial stock were to be sent to German boarding schools and subsequently made available for adoption by the families of SS members, with their Polish origin to be concealed from any prospective parents. After World War II, Greifelt was arrested in May 1945. Greifelt was sentenced to life imprisonment at the RuSHA trial on 10 March 1948. He had been found guilty as the person mainly responsible for the expulsion of people from Slovenia, Alsace, Lorraine and Luxembourg. He died in custody in the prison for war criminals in Landsberg. Greifelt argued in his defence that he had the welfare of the people whom he expelled at heart and wanted to help them to find "the consolidation of their existence and thereby of their Germanism." His claims were rejected however and he was sentenced under recently passed genocide legislation.
