Upon his return to Serbia, his whirlwind military career began: from a sergeant in an artillery regiment, he was promoted to head of the General Staff Section and Chief of the Ministry of the Military by 1910. In the same year, he was appointed a military envoy to St. Petersburg, where he remained until the beginning of the Second Balkan War. After returning to Serbia, he took command of the Drina Division, which distinguished itself in the Battle of Bregalnica. In the Great War, he first led the Šumadia Division in combat in Mačva, and in August 1914 he was appointed Chief of Staff of the First Army. After retreating to Corfu, Hadžić was given a duty that would mark his further life. Pursuant to the decree of the Minister of the Military of 24 February 1916, namely, the formation of the 1st Regiment of the Serb volunteer detachment. Composed of Serbian POWs, formerly in the ranks of the Austrian Army and originally from Serbian lands of the Habsburg Empire, volunteered "en masse" and in February the First Serbian Volunteer Division numbered almost 10,000 men in Russia, with Colonel Hadžić appointed as its commander. Hadžić arrived in Corfu, accompanied by 21 officers and just as many lower ranks, on a new duty in Odessa on 23 April 1916. Volunteers still continued to come and by mid-August (1916), the division had nearly 18,000 men.