Petrescu-Comnen's career took an upward turn after Romania entered World War I, initially as a noted campaigner for the cause of Greater Romania; he was also tasked with explaining Romania's capitulation. According to Duca, Comnen, "whose precarious health had exiled to Switzerland", matched and surpassed Drăghicescu's similar work in France. He displayed "exquisite skills as a propagandist". He cultivated the friendship of Transylvanians in exile, in particular Aurel Popovici and Iosif Șchiopu, who became his trusted advisers. Initially, Comnen contributed to the cause from a Swiss sanitarium, where he was recovering, hoping to carry forward Popovici's work after the latter had died. With articles in , and with tracts such as ("Notes on the Romanian War"), he complained about the Entente Powers "sacrificing Romania" after the October Revolution. French scholar Marcel Emerit found his a biased, "unilateral", perspective, containing "a lively condemnation" of the Russian Republic. Comnen also contributed an ethnographic overview of Dobruja ("La Dobrogea"), just as the region was being absorbed into a Greater Bulgaria. Georges Lacour-Gayet, who presented the work at the Romanian Academy, noted that the "savant work" of "truth and justice", had exposed the practices of Bulgarization.