He was born in Vicovu de Sus, now in Suceava County, Romania, and graduated with a law degree from the University of Vienna. At the end of World War I, he advocated a division of the province of Bukovina along ethnic lines, into a Romanian-controlled southern Bukovina, and a Ukrainian-controlled northern Bukovina. The borders envisioned by Onciul and his Ukrainian counterparts correspond roughly to the present Romanian–Ukrainian borders in Bukovina.
As the Austrian governor surrendered power to Onciul in 1918, he and the Ukrainians proceeded to divide the former province between themselves much as Onciul had previously envisioned.[1][2] His rival Iancu Flondor, leader of the National Party, denounced Onciul's intentions and proceeded to demand the intervention of Romania, putting an end to the agreement by Onciul and the Ukrainians regarding Bukovina. With Romanian troops securing the region, Flondor called on a General Congress of Bukovina, where members of various ethnicities, except Ruthenian, decided on an unconditional union with the Kingdom of Romania.
