After the Annexation Crisis of 1908, the organization Narodna Odbrana was founded in Belgrade, which recruited and equipped volunteers and formed Chetnik detachments for the upcoming liberation wars.

She managed to convince them to let her join a Chetnik unit during both Balkan Wars,[2] She joined the Serbian Army under the male name Sofronije Jovanović immediately upon the start of World War I and the first attack of Austria on Serbia.

In July 1914, as part of the Srem Volunteer Detachment, she commanded the first group of Serbian fighters who crossed the Sava to Srem to reconnoiter enemy positions and cut telephone wires to Zemun, interrupting the Habsburg communications.

She then fought with the Serbian army during the breakthrough of the Salonika front and the subsequent liberation of Serbia and Belgrade in November 1918.

[1] She was nicknamed La Jeanne d'Arc Serbe (The Serbian Joan of Arc) by French reporters.