In 1918, he married Cornalia Slot, with whom he had three children.
From 1925 to 1929, Popitz acted as State Secretary in the German Ministry of Finance, where he sometimes worked under Finance Minister Rudolf Hilferding, with whom, in 1929, he was provisionally retired owing to political differences with the government.
As an honorary professor of tax law and financial science at the University of Berlin and the State Academy (Verwaltungsakademie) from 1922, Popitz was named to Kurt von Schleicher's cabinet as State Minister without Portfolio, and as commissary leader of the Prussian Finance Ministry.
On 21 April 1933, Popitz took up the offices of Prussian State and Finance Minister, although up to this time, he was still not a member of the NSDAP. On 1 February 1937 (1939, according to some sources), the Völkischer Beobachter reported in its South German edition that Popitz had been offered the NSDAP's golden insignia, which he had accepted.
As a rightwing conservative and monarchist who would have preferred to see Crown Prince Wilhelm, Kaiser Wilhelm II's eldest son, succeed Adolf Hitler, Popitz became active in the resistance circles beginning in 1938, including the group around Carl Friedrich Goerdeler. As a member of another such circle, the Mittwochsgesellschaft ("Wednesday Society"), a small group of high officials and industrialists who had evolved from a debating club into a centre for conservative opposition to the National Socialist régime, he was drawn ever further into the centre of the conspiracy against Hitler. He drew up a provisional post-Hitler constitution, the Vorläufiges Staatsgrundgesetz, whose general tendencies were quite authoritarian.
In the summer of 1943, Popitz conducted secret talks with Heinrich Himmler, whose support he sought to win for a coup d'état, and whom he tried to convince to take part in attempts to negotiate with the Western Powers for an acceptable peace deal.
Already in the autumn of that same year, Popitz was being watched by the Gestapo, and indeed, he was arrested in Berlin on 21 July 1944, the day after Claus von Stauffenberg's unsuccessful attempt on Hitler's life at the Wolfsschanze in East Prussia. After his arrest, Popitz told the Gestapo:
“As somebody who was very familiar with conditions in the System period [i.e. the Weimar Republic], my view of the Jewish question was that the Jews ought to disappear from the life of the state and the economy. However, as far as the methods were concerned, I repeatedly advocated a somewhat more gradual approach, particularly in light of diplomatic considerations”
Popitz went to tell the Gestapo that:
"The Jewish question had to be dealt with, their removal from state and economy was unavoidable. But the use of force which led to the destruction of property, to arbitrary arrests and to the destruction of life could not be reconciled with law and morality, and, in addition, seemed to me to have dangerous implications for people's attitudes to property and human life. At the same time, I saw in the treatment of the Jewish Question a great danger of increasing international hostility to Germany and its regime"
On 3 October, he was sentenced to death at the Volksgerichtshof by Roland Freisler. At first, in the hopes that the contacts with the Allies that he and Popitz had discussed might still develop, Himmler saw to it that Popitz was not put to death. However, as it became apparent that no such talks would be forthcoming, Popitz's fate was sealed. He was hanged on 2 February 1945 at Plötzensee Prison in Berlin.
- Noakes, Jeremy Nazism, Volume 4, Exeter: University of Exeter Press, 1998 pages 632-633
- Noakes, Jeremy Nazism, Volume 4, Exeter: University of Exeter Press, 1998 page 633
Works by Popitz
- Finanzausgleichsprobleme. - Berlin : Dt. Kommunal-Verl., 1927
- Der künftige Finanzausgleich zwischen Reich, Ländern und Gemeinden. - Kiel : Bibl. d. Inst. d. Weltwirtschaft, 1955 <Repr. d. Ausg. Berlin 1932>
Works about Popitz
- Lutz-Arwed Benthin: Johannes Popitz und Carl Schmitt: zur wirtschaftlichen Theorie des totalen Staates in Deutschland. - München : Beck, 1972. - (Münchener Studien zur Politik; 19) - ISBN 3-406-02799-7
- Hildemarie Dieckmann: Johannes Popitz: Entwicklung und Wirksamkeit in der Zeit der Weimarer Zeit. - Berlin : Colloquium Verl., 1960
- Biography at DHM.de (German)