The Transylvanian coal-mining center of Petrozsény (Petroșani) was occupied by the Romanian Army on 29 August, two days after the Kingdom of Romania declared war on Austria-Hungary.

[1] The central column of General Ioan Culcer's Romanian 1st Army advanced into a region of valuable coal mines, whose output was crucial to the Hungarian railway system.

[4][5][6] The Jiu Covering Force, consisting of the 21st Infantry Brigade of the 11th Division, crossed the border at the Vulkán and Szurdok passes and occupied the vital Transylvanian coal-mining center at Petrozsény on 29 August.

[7] By 3 September, this group of General Culcer's Romanian 1st Army occupied the important coal area between Hobicaurikány (Uricani) and Petrozsény, driving back the ineffective Landsturm and miners battalions of the 144th Infantry Brigade over the saddle of Merisor.

[11] Due to its valuable coalmines, the area occupied by the center of General Culcer's 1st Army was the first location of any military or commercial value to fall into Romanian hands.