During World War I, Florian served in the Romanian Land Forces and was taken prisoner by the Germans. He was transported to an internment camp at Krefeld, alongside figures such as Alexandru D. Strurdza and Ilie Moscovici. Eventually, Florian was freed by his captors and allowed to lecture at King Carol Foundation in Bucharest, under a German occupation government. As Florian later indicated, this was made possible by the intercession of a Germanophile scholar, Alexandru Tzigara-Samurcaș, who vouched for him, and by the protection of Constantin Giurescu. Following the November Armistice, which reinstated the pro-Allied government, Florian, Tzigara-Samurcaș and Rădulescu-Motru were all subject to an official inquiry, and accused of being collaborators. The University Commissions created for this task were largely ineffective, and, among the incriminated, Florian was one of few who presented himself for questioning.