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Nieland was drafted into the Imperial Army in June 1918 just after his final examinations at modern grammar school. He remained a soldier until one month after the end of World War I (discharge in December 1918). From February 1919 he studied jurisprudence and economic science in Göttingen and Hamburg. After the end of his studies in July 1922 he worked as a commercial clerk for three years in two Hamburg export firms. Hereupon followed a job training in the local and provincial administration. Afterwards Nieland went to the small town Kirchhörde (which now forms part of Dortmund) as a candidate for the career of a Westphalian bailiff. His political career started as a head of the district authority in his native town Hagen, later on Nieland became district president in Münster. In June 1925 he completed his political science dissertation on the topic "The power as a governmental concept of law: at the same time an analysis of the German Reich's constitutional law situation under the rule of the Versailles Treaty" (German: "Die Macht als staatlicher Rechtsbegriff: Zugleich eine Untersuchung über die staatsrechtliche Stellung des Deutschen Reiches unter der Herrschaft des Versailler Vertrages").
In January 1926 Hans Nieland joined the NSDAP (membership number 33 333), became Bezirksführer (English: District Leader) at home and then Sektionsführer (English: Section Leader) in Hamburg. Moreover, he entered the SS (membership number 61 702), was promoted SS Major General Brigadeführer on January 30, 1939 and achieved his assignment to the Staff SS Upper Sector "Elbe" (German: Stab SS-Oberabschnitt "Elbe") on November 9, 1944. From November 1926 until March 1928 he applied himself to law studies again in Münster and Göttingen. In December 1928 he became an intern with the Altona legal authorities. On September 14, 1930 he was elected Member of the Reichstag for the Hamburg constituency.
On May 1, 1931 Hans Nieland was appointed Leader of the NSDAP Foreign Organization (German: NSDAP Auslands-Organisation, abbreviated: NSDAP/AO), which was founded in Hamburg, by NSDAP Reichsorganisationsleiter (English: Reich Organization Leader) Gregor Strasser. Nieland already resigned from this party office on May 8, 1933 because he had acceded to more important duties in the meantime. As from March 5, 1933 he was head of the Hamburg police authority for a short time and since May 18, 1933 member of the Hamburg provincial government. Nieland assumed the Hamburg revenue office in May 1933. Additionally, he directed parts of the Administration for Economics, Technology and Labour since November 1934. After the Groß-Hamburg Gesetz came into force in April 1937 Nieland was awarded the title Senator and the position of a city treasurer for life. In February 1940 he was appointed Lord Mayor of regional capital Dresden at the suggestion of Reichsstatthalter (English: Imperial Governor) Martin Mutschmann by Reich Minister of the Interior Wilhelm Frick. After the heavy air raids of February 13 and 14, 1945, which destroyed the baroque historic section totally, Nieland left precipitously Dresden on February 23, 1945, disappeared completely for 8 days and turned up in Berlin on March 3, 1945.
From June 2, 1945 until February 21, 1948 Nieland was detained in several British detention centers, for example in Neumünster-Gadeland and in Civil Internment Camp No 5 Staumühle (near Paderborn). In August 1948 a fine was imposed on Nieland in the course of a "Spruchkammerverfahren" (English: "proceedings before denazification tribunals") in Bielefeld, which was regarded as compensated by the term of imprisonment, however. In 1949 he was classified as minderbelastet (English: marginally incriminated) and in 1950 as Mitläufer (English: follower or nominal member).