He joined the military school in 1854, becoming an artillery sub-lieutenant in 1859. As a captain, he took part in the coup of February 11, 1866, that toppled Alexandru Ioan Cuza, the ruling Domnitor of the United Principalities. In 1867, he resigned from the Romanian Army and started two newspapers: Perseverenţa and Democraţia, in which he supported democratic ideas. Considered a "political agitator", he was arrested three times, including once in Austria-Hungary, where he was imprisoned for several weeks in the fortress of Arad.
In August 1870, he took part in the republican insurrection against the HohenzollernDomnitor, Carol I, in Ploieşti. The movement was suppressed and he was charged along with 40 other people, but the Târgovişte court of law acquitted them. In his tongue-in-cheek account of the insurrection (Boborul), Ion Luca Caragiale named Candiano-Popescu as "President of the Republic", and claimed that he had appointed several of his collaborators into high office.