At the outbreak of the First World War, Reinhardt was staying in Riga, Livonia, and he ended up spending the war in an internment camp in Siberia as an enemy alien. In 1919, he was the headmaster at the Thuringian Commercial School, and in 1924, he founded the first German Long-Distance Commerce School. He was also an administrator at the Thuringian State Finance Office. In October 1926, he joined the Nazi Party and quickly built up a career with them with his talent for speaking and his knowledge of economic and taxation systems. In the same year, he became the Local Group Leader in Herrsching, in 1927 the District Leader in Upper Bavaria-South, and in 1928 to 1930 the Upper BavariaGauleiter. From 1928 to 1933, Reinhardt was the leader of the Nazi Party's Speaking School, and 6000 party members then received propagandistic schooling. In 1930, Reinhardt became a member of the Reichstag and took on the leading role in the NSDAP in financial issues. In 1933, he became an SAGruppenführer and a member of the staff Adolf Hitler's deputy, Rudolf Hess. On 6 April 1933, after Hitler's intervention, Reinhardt became State Secretary in the Reich Ministry of Finance under Johann Ludwig Graf Schwerin von Krosigk succeeding Arthur Zarden, whose incumbency violated Nazi policy, as he was Jewish. In 1937 came Reinhardt's appointment as an SA Obergruppenführer.
State Secretary
Reinhardt could count on the Nazi Party's and Hitler's backing, which was why he held such an influential position from the outset. Reinhardt made the decisions as to taxation. Under him were the Tax and Customs School – set up by him in 1935 – and the Zollgrenzschutz. It was one of the components of the programs aimed at reducing unemployment, which collectively were also known as the Reinhardt Program. It is held by some, particularly German, historians that Reinhardt gave his name also to Operation Reinhard, although broader understanding especially after its termination has associated that program's name with Reinhard Heydrich, first head of the RSHA. The confusion stemmed from the fact that Heydrich had spelled his first name both Reinhard and Reinhardt throughout the 1930s during his career in the SS. Section 1 of the Tax Reconciliation Act of October 1934 traces to Reinhardt. This law implemented the Nazi Weltanschauung. It obviated numerous, detailed changes to the individual regulations and implemented the Nazi ideology in one stroke. In the time that followed, a whole series of further regulations and decisions against Jews bore Reinhardt's signature, for instance, 1942's statement on stolen gold from dispossessed and murdered Jews. He was publisher of the Deutsche Steuerzeitung, which, along with all his other publications, he made required reading for all finance officials.
Reinhardt was captured by the Allies in 1945, and on 17 June 1949 he was classified as a Hauptschuldiger at a Denazification proceeding, and sentenced to four years in labour prison. In an appeal proceeding late in 1949, the sentence was upheld, but the penalty reduced to three years. By late 1950 the sentence was definitively confirmed. Reinhardt's time in custody was to be counted towards his penalty, which led to his immediate release. In the court proceedings, Reinhardt saw himself in the role of a financial expert who was limited to Reich finances, mitigated penalties inflicted on Jews, and otherwise had to bend to other ministries' decisions.
