After training as a metalworker in Grivița, he took to left-wing politics, joining the underground communist groups at some point before the railwaymen's strike of February 1933, which he helped organise together with Constantin Doncea and Gheorghe Vasilichi.

He helped rallying up Romanian prisoners of war for the Red Army's Tudor Vladimirescu and Horea, Cloșca și Crișan Divisions, emerging as a political commissar and lieutenant colonel.

He followed the Romanian army and the Vladimirescu units as they crossed into Northern Transylvania and Hungary, recording his troops' initial bravery and subsequent breakdown during the Battle of Debrecen.

Although promoted to major general in 1948, and assigned seats in the Great National Assembly and the Central Committee, Petrescu was pushed aside by the Romanian People's Republic; he had only a brief involvement in the collectivisation of agriculture, as part of a commission that also included Pauker.

[14] A report by Siguranța agents suggests that non-communist members of the Grivița union regarded Petrescu and the others as their fellow workers, seeing them more favourably than "actual communists" such as Petre Gheorghe.

[15] A participant in the events, Vasile Bâgu, recalled in 1958 that Petrescu was involved in a warning strike of 28 January–2 February 1933, when he and Doncea, alongside Petre Gheorghe and Hugo Barani, were elected to a committee which presented the workers' demands to the CFR management.

Held on Hagi Tudorache Street near Herăstrău, it supposedly "established measures which imposed themselves [...] after government had refused to acknowledge progress made by the strikers on 2 February, and had sealed of the revolutionary unions' house.

[3][22] Sociologist Vladimir Tismăneanu argues that Petrescu also spent time in Doftana Prison, where he became a supporter of Gheorghiu-Dej, who had also been prosecuted for the Grivița strike, and who was emerging as leader of a PCR faction.

[25] Witnesses for the defence included a right-wing former minister, Mihail Manoilescu, who argued that the CFR workers had reason to be upset by the violation of their labour rights, as well as by government inaction in their favour.

[28] In various issues between September 1933 and January 1934, the PCR's illegal newspaper, Scânteia, declared that Petrescu and Doncea were victims of "fascist terror", drawing a parallel between their prosecution and the Leipzig Trial in Nazi Germany.

[30] In his coverage of the trial for Adevărul daily, left-wing journalist Alexandru Sahia argued that both Doncea and Dumitru Petrescu had been found guilty of "instigating premeditated murder", but that the charge referred to a co-defendant, Georgescu Ghebosu, who had been accused of distributing cold weapons to the strikers, and of advising them to stand their ground.

[35] The escape took place on 3 January 1935,[14] when Petrescu's wife Ecaterina ultimately arranged for a getaway car to wait them as they went out for a morning walk—"the driver being recognisable for his holding a white flower."

[11][51] As Șperlea writes, this activity included "touring the Romanian prisoner of war camps for a precise reason: to convince them that they should fight alongside the Red Army so as to bring down what they called the 'fascist Antonescian' regime.

[55] In November 1943, after managing to recruit the entire population of a camp into a battalion, he was faced with insubordination by the newly-appointed commander, Boțoacă, who resented the red star insignia added on their Romanian uniforms.

[58] On 1 December 1943, Petrescu was moved from the DTV to a parallel military unit, which was later known as the Horea, Cloșca și Crișan Division (DHCC), wherein he was a lieutenant colonel, tasked mainly with propaganda work.

[63] On 29 September, Petrescu was at Holod, writing to Pauker that his unit had behaved "very well", but asking that the PCR intervene to curb Soviet arrogance, as well as to done down perceptions of the DVT as a "communist outfit".

[73] He was assisted at the ECP by Corneliu Mănescu, who, despite being considered a political suspect, had escaped the "verification" campaign and was helping Gheorghiu-Dej form an independent connection between the PCR and the Chinese Communist Party.

As Gîju writes, these initiatives, which resulted in the creation of an army's sports base—as CSA Steaua București—, were troubling, since they came at a time when Romania had been strapped by the Soviet Union with orders to pay reparation for the previous war.

[79] Petrescu held on to his ECP position before and during the establishment of a Romanian People's Republic on the early days of 1948—a stage when the PCR went as the "Workers' Party" (PMR), to signal its absorption of the PSDR.

"[81] Petrescu ran in the legislative election of March 1948 on the People's Democratic Front (FDP) list, serving one full term in the Great National Assembly (MAN)—wherein he represented Gorj County.

[83] Shortly after, Chirtoacă reported complaints made privately by the more liberal communist Ion Gheorghe Maurer, who allegedly described collectivisation as a disaster which had caused peasants to "hate us all".

[85] Petrescu's military career saw his promotion to major general on 25 July 1948, when he was also assigned to work directly under the secretariat of the National Defense Ministry; before or after that date, for a few months, he was head of the Army's Political Directorate.

[87] In June–July 1949, he returned to Moscow with a PMR delegation that also comprised Drăghici, Leonte Răutu, Simion Bughici, and Raia Vidrașcu; its mission was to study and copy the organizational methods of the Soviet Communist Party.

"[5] Câmpeanu assesses that, overall, Doncea and Petrescu were assigned "utterly mediocre" positions, and effectively sidelined, by Gheorghiu-Dej, who had been made General Secretary after having spent the war years in Romanian prisons.

[98] On 16 October 1952, the workers at Tudor Vladimirescu Textile Mill in Tîrgu Jiu nominated Petrescu as their FDP candidate in the upcoming legislative election;[5] he took that seat, one of 37 for Craiova Region, on 30 November.

On that occasion, "he spoke about the courage shown by railway workers under the direct leadership of the Communist Party of Romania and Comrade Gh[eorghe] Gheorghiu-Dej in these battles for a better life and against fascism.

[106] His term was ultimately cut short by the peaceful purge, consecrated on 17 April 1956, when the entire Politburo asked him to step down and take up "grunt work" (munca de jos).

[113] One account provided by Tismăneanu and historian Cristian Vasile centers on Petrescu and Doncea's archival interview with Mihail Roller, which fully recorded their doubts about Gheorghiu-Dej's contribution to the 1933 strike.

[130] This was the only body of power wherein Ceaușescu still tolerated old communists, namely those who had been active with the PCR during its underground phase; even here, there were only four: Petrescu, Maurer, Emil Bodnăraș, and Gogu Rădulescu.

[3] On 14 September, the body was retrieved from Prague by Virgil Trofin and Florian Dănălache, and accompanied to Ruzyně International Airport by Evžen Erban and other Czechoslovak Communist Party dignitaries.