Diamandy was also a member of the Bârlad National Romanian Committee, which gathered funds and artifacts for the Romanian delegation to the 1889 Exposition Universelle. He was working on a novel in the manner of Émile Zola, which, according to Gorovei, was over-detailed and boring. Upon graduation, Diamandy volunteered for service in the Romanian Land Forces, spending a year and a half as an artillery man. Disliked because of his pranks ("which I for one found spirited"), he was moved to the 7th Artillery Regiment in Călărași, and, because once there he complained about the mistreatment of regulars by the officers, spent several months in the disciplinary barracks. He notes: "Just as I was ending my term as a volunteer, the captain, having learned that I had donned a civilian's outfit for a private party, ordered me in lockdown.—Lockdown meant no stove and no windows, so that's how I ended up with pneumonia." Diamandy went on to study Law at the University of Paris, but did very poorly, and was only granted half of his license; he completed the rest at Caen University. He pursued other scholarly interests, becoming a corresponding member of the "Société Anthropologique". He published notices on Cucuteni, as well as studies on Bulgarian handicrafts and a sketch of Romanian anthropological criminology. He also completed, in 1891, the historical demography tract "Dépopulation et repeuplement de la France" ("The Depopulation and Repopulation of France"). In parallel, he resumed his work in political journalism, with articles published in "Le Journal", "La Petite République", "La Justice", "Le Socialiste", and "L'Art Social". Taking over for the Romanian "revolutionary socialist" cell founded by Mircea and Vintilă Rosetti, he joined the "internationalist revolutionary student group" of the Latin Quarter, presided upon by Alexandre Zévaès. He was one of its delegates to the 1891 International Socialist Labor Congress in Brussels. According to his own account, he presided over the Congress proceedings. In December of that year, Diamandy sided with Zévaès' moderate leadership against the radical revolutionary minority. The next year, in May, having been elected President of the student group, he was also delegated to the socialist feminist congress, where he obtained a nominal submission of socialist women to the program of a future internationalist party.