The scion of a Hungarian Jewish and working-class family, he was child laborer who acquired skills in metallurgy, moving from his native Nagyvárad (Oradea) to Budapest.
His contribution in the field of socialist propaganda made him a political suspect by the time of World War I, and he was punished with conscription into the Hungarian Landwehr—though he continued to proselytize among his fellow soldiers.
Breiner was enthusiastic about the Aster Revolution, and went on to fight for the Hungarian Soviet Republic, resulting in his brief imprisonment by the Romanian Land Forces during the expedition of 1919.
Upon release, he traveled clandestinely into the Soviet Union, where he participated in the PCR's fifth congress—which confirmed his own induction by the party secretariat, as well as his role in editing Scînteia, the underground newspaper.
From 1937, Breiner served as the senior member of a triumvirate party leadership, alongside Ștefan Foriș and Ilie Pintilie; he himself spent most of 1938 in Moscow, seeking (and finally obtaining) recognition from the Comintern.
Himself disgraced by Soviet political realignments, Stefanov ultimately abandoned his position as general secretary in 1939, leaving Breiner to take over in a provisional capacity.
[1] Upon being recognized as a journeyman at the age of sixteen, he could also join the trade union; shortly after, he also entered the Social Democratic Party of Hungary (MSZDP).
[1][5] During the earliest stages of World War I, Breiner was employed at one of the major metallurgical plants on Csepel, in southern Budapest, and was recognized by the local branch of the MSZDP as a reliable cadre.
[1][5][7] He joined the PCR upon its creation as a legal party, in 1921,[1][7] and was its main activist until October 1923, when Rozvan, returning from a tour of Transylvania, assumed the position of a local leader.
[1][5][7][11] In March 1926, during court proceedings involving almost 100 PCR defendants, Breiner was tried in absentia, and sentenced to a five-year term on charges of having "infiltrated" Romania as a foreign agent.
[14] One of Breiner's official biographies claims that torturers were specially brought in from Bucharest, and that, despite being subjected to "barbaric" torments, "he never gave them any of his comrades' names".
[5][7] Before the strike had broken out, Breiner himself had been detained: in April 1932, he was picked up alongside fellow activist Pavel Bojan after a sting operation on Rozelor Street, Bucharest.
[18] In May, a mandate for his arrest was upheld by the Ilfov County tribunal, which followed up on accusations that he had circulated "subversive manifestos" alongside comrades Árpád Weiss and Moscu Parlacu.
[25] With much of the party now arrested or self-exiled in Soviet territory, the Comintern intervened to depose the PCR secretariat; in May 1937, Breiner, alongside Foriș and Ilie Pintilie, received a mandate from Moscow to organize a new executive body.
[31] Breiner also described the communist platform as defending the "brilliant Soviet people" against the threat of a "criminal war" by its capitalist adversaries, while supporting the future dismemberment of Greater Romania as a way to liberate "oppressed nationalities" within the country's borders.
Again seconded by Foriș and Pintilie,[11] he planned a rescue operation which, if carried out, would have resulted in Gheorghiu-Dej escaping Doftana alongside other inmates; he also supervised the Union of Communist Youth, and, in June–July 1939, personally educated its cadres (including Nicolae Ceaușescu) at a secret location in Ploiești.
[11] The Comintern eventually recognized Breiner as provisional general secretary in 1939, after Stefanov had been condemned by the Soviet leadership (which had just ratified the Molotov–Ribbentrop Pact) for being too focused on defeating fascism.
[38] Before her marriage, Piroska had received attention for putting out revolutionary propaganda addressed to the workers at Bucharest's Lemaître Factory;[39] she had afterward served time in prison, where she is said to have been "beat[en] with rubber batons on her stomach".
One of the latter was Ovidiu Șandru, who tried to hold an impromptu speech about Breiner's activity in the labor movement—he was forced to step down by the other participants, who feared that any revolutionary message would provoke a violent response from the authorities.
[43] The Comintern eventually became aware that the PCR had virtually no executive leadership during the great upheavals caused by the FRN's downfall and the emergence of a National Legionary State.
[45] As reported by communist militant and period witness Pál Veress, "only a hair's breadth separated [them] from being executed by Antonescu's firing squad".
The printing company of Sonnenfeld & Friedländer was nationalized in 1948, and immediately renamed after Breiner;[47] the same occurred at the Volna Metallurgical Plant in Brașov[48] and at the former Magyar–Belgian Textile Mill in Cluj.
[58] The trend was reversed after the Romanian Revolution of 1989: the Dobroteasa street was renamed after poet Ion Minulescu in January 1991,[59] and a commemorative plaque was similarly removed.