Career
A year later, in 1912, Nistor moved to Czernowitz, to hold the chair of Southeastern European history, but after the start of World War I, he moved to the Romanian Old Kingdom, where he published various studies on the history of Bukovina. He was elected a member of the Romanian Academy in 1915. He also authored an ethnographic map of Bukovina under Austrian domination (see Cisleithania), based on the census of 1910.
Living in Iași by the time Romania entered the war on the Entente side, Nistor left Romania at the climax of the Romanian Campaign, when troops of the Central Powers threatened the region. In July 1917, he moved to Odessa, in territory held by the Russian Provisional Government, and began teaching Romanian history to the (mostly Bessarabian) students at the University of Novorossiya. He interrupted the course in November 1917, after a group of armed Russian revolutionaries broke into the university building. Nistor was, however, safely escorted outside by some of the Bessarabian soldiers who were part of his audience.
In February 1918, together with other Austro-Hungarian refugees (including Octavian Goga), Nistor departed for Ovidiopol, Cetatea Albă, and then finally reached Chișinău. He stayed in the city, where he argued for the founding of a Moldavian University, and soon began lecturing on the History of the Romanians. He used the data gathered from the Chișinău Archives to write the History of Bessarabia, published in 1923. Nistor also witnessed the Sfatul Țării session which voted the union with Romania.
After the war ended, he returned to his native Bukovina and was one of the members of the National Assembly of Bukovina in Cernăuți who voted for the union with Romania on November 28, 1918. Nistor was also one of the fifteen Bukovinians who presented the Union Act to Romania's King Ferdinand I.
Nistor presided upon the Democratic Union Party, which had a centralist agenda. Between December 18, 1918 and May 2, 1919, he was a member of Greater Romania's Ion I. C. Brătianu government, as a Minister for Bukovina, and, between February 14 and February 27, also held the rank of minister for Bessarabia, while the nominal minister was delegated to the Paris Peace Conference. Between May 1920 and January 1922, Nistor was a Senator in the Parliament of Romania.
In the interwar period, Nistor wrote many historical works, including The Origin of Romanians and the Vlachs of Thessalia and Epirus and The History of Romanians in Transnistria (1925). He was also the director of the historical magazine Codrii Cosminului, which was published between 1924 and 1939.
Elected rector of the University of Cernăuți in 1920, serving as such until 1921, and again from 1933 to 1940. Also in 1920, he joined the National Liberal Party (PNL), and was again the Minister of State for Bukovina in the Sixth Ion I. C. Brătianu cabinet (1922–1926), Minister of Public Works in the Vintilă I. C. Brătianu cabinet (1927–1928), Minister of State and then Labour in the First Tătărăscu cabinet (1934), and Minister of Labour in the Second Tătărăscu cabinet (1934–1935). In 1938, he broke with the PNL and sided with the National Renaissance Front regime established by King Carol II, and was Minister of Religious Affairs and the Arts in the Fifth Tătărăscu cabinet (November 24, 1939 – May 10, 1940). As a politician, he strongly opposed communism, social democracy and fascism.
Starting October 1940, under the National Legionary State, Nistor taught at the University of Bucharest, becoming the target of Iron Guard persecutions for the support he had given to King Carol. Following the Guard's defeat during the Legionnaires' Rebellion of 1941, he sent a congratulatory telegram to Conducător Ion Antonescu. He was pensioned in the same year, and, starting 1943, he was in charge of the Library of the Romanian Academy. Nistor kept the latter office until after the establishment of the Communist regime, when the purge of anti-communists in the Academy began (1948).