[2] During the 1922–1923 academic year, Mironovici was involved in organizing a student strike in support of a numerus clausus, which succeeded in preventing the start of lectures in June 1923.

[4] The Văcăreșteni were eventually acquitted on a technicality, with the group's defence lawyers arguing that, since none of the students were public officials, they could not be charged with treason or "inciting revolution".

[2] During their imprisonment, the group — most of whom were involved in the National-Christian Defense League ("LANC") — decided to form a new ultranationalist youth organization, inspired by an icon of the Archangel Michael located in the prison.

Codreanu was arrested and, as collateral, Mironovici, Moța, Gârneață, and Popescu were detained for two months at Galata prison, during which they undertook a hunger strike.

[7][8] In November 1927, Mironovici, alongside Codreanu, Moța, Gârneață, Gheorghe Clime, and Corneliu Georgescu, among others, took an oath as a founding member of the Legion of the Archangel Michael, which would later be known as the Legionary Movement or the Iron Guard.

[9] In December 1936, establishing the highest grade in the Legionary hierarchy, Codreanu named Mironovici (as well as Moța, Georgescu, and Gârneață) to the rank of "Commandant of the Annunciation" ("Comandant al Bunei Vestiri").

In February 1938, King Carol II seized emergency powers, suspending the constitution and creating a royal dictatorship, enforcing a ban on the Legionary Movement.

He is buried at Țigănești alongside his wife, Elena, in front of a wooden cross co-dedicated to Mironovici and Legion co-founder Corneliu Georgescu.