Frățiman welcomed the union of Bessarabia with Romania in 1918, being an outspoken in his adversity toward Bolshevik Russia; in parallel, he supported autonomy for the Chișinău Archbishopric within the Romanian Orthodox Church.

As reported by the latter, Frățiman debated the other two in a philosophical quarrel, founding a school of through that Halippa knew as "Frațmanism" (though Popovschi could not remember its ideological nature beyond its stated opposition to the official textbook, authored by Pyotr Kudryavtsev).

[11][12] Frățiman began his teaching career in 1899, when he was appointed tutor of Greek at the Theological Seminary in Pskov; in June 1904, he took a similar posting in Lyskovo, but left to take up an administrative position in Saint Petersburg.

[17] His training allowed him to teach religion, French language, and world history; his brother Petru had similar interests and, in 1904, helped establish the Bessarabian Historical and Archeological Society.

[11] In summer 1916, Russian officials had him detained at the penitentiary of Soroca, and subsequently deported to Central Asia, in Turgay Oblast;[21][22] some authors suggest that he was also held in Siberia.

"[28] Returning to Bessarabia that July, Frățiman joined a corpus of teacher tasked with Romanianizing Bessarabian schools, which included the adoption of Latin spellings; he also taught the history of Romania.

[30] Still pursuing an interest in the study of local history and ethnology, he helped establish in early 1918 a Historical and Literary Society (named after Bogdan Petriceicu Hasdeu), and was admitted into the Romanian Academy of Bucharest.

In June, he traveled to Iași as a delegate of Chișinău Archbishopric, negotiating the return of Bessarabian parishes under the authority of the Moldavian Metropolis within the enlarged Romanian Orthodox Church.

Frățiman and his colleagues attempted to preserve some administrative rights for their regional church, but were instantly rebuked by Metropolitan Pimen, who asked that they submit to the Romanian state in all matters, including religious.

[35] During elections in November 1919, Frățiman tried but failed to win a seat in the Deputies' Assembly, enlisting with the minor Independent Party of Bessarabia alongside Ludovic Dauș, Sergiu Niță, and Constantin Stere.

[37] In December 1919, he was also co-opted by the Cultural League for the Unity of All Romanians, joining its local executive committee—where he served with Romulus Cioflec, Paul Gore, Alexandru Ouatul and others.

[38] He eventually returned to settle in Chișinău, where he taught at the Teacher Seminary for Girls; he was not considered for a position at the new Theology Faculty of Iași University, which was operating in the same city.

[39] Frățiman's sympathies soon veered into far-right politics—on December 15, 1920, he joined Nicolae Negru's League of Christian Bessarabians, which also recruited former members of the Union of the Russian People.

[40] As noted by fellow historian Nicolae Iorga, Frățiman's academic work comprised studies "of small proportions", but showed his "deep familiarity with sources dealing on the life of his own people, on either side of the Dniester.

[45] In November 1926, Pan Halippa employed Frățiman at Astra cultural society's Bessarabian Literary and Philological Section, where he worked alongside Paul Gore.