During World War II, Petre Borilă resided in the Soviet Union, where he was still present as Romania joined the Axis Powers in the 1941 invasion. He worked for the Comintern before its 1943 dissolution, being a personal collaborator to its leaders, Georgi Dimitrov and Dmitry Manuilsky. At the time, he also had close contacts with other prominent Romanian communist exiles, including Luca, Pauker, Leonte Răutu, and Valter Roman — this nucleus – "the Muscovite faction" – representing a distinct group inside the PCR, planned to take over the entire party upon their return to Romania. In this, they were opposed by the "prison faction", whose members, including its leader Gheorghe Gheorghiu-Dej, had been arrested and were serving time in Romania. According to historian Vladimir Tismăneanu, Borilă had grown aware that support for his faction was fragile, and, in order to ensure his political survival, chose to always maintain close contacts with Gheorghiu-Dej.