[2] Kirhner finished the Military Academy in Vienna, then served in the Austro-Hungarian army as an officer in Vinkovci in the Kingdom of Croatia-Slavonia (now Croatia) for seven years.
[2] According to unconfirmed stories of his comrades, he had deserted after killing a superior officer who, knowing of Kirhner's ancestry or not, had talked very insulting and degrading about Serbs.
[2] Kirhner joined the Serbian Army, being accepted by decree by King Peter I of Serbia.
[2] According to unreliable stories, Kirhner fled to Serbia swimming across the Sava river to Belgrade in the summer of 1914, and was the first to bring news that the Austro-Hungarian government was ready to declare war regardless of the response to the July Ultimatum.
[2] In 1914 he participated in the capture of an Austro-Hungarian military post on the left shore of the Sava, during which he was wounded in the right foot, but declined to go to hospital.
[2] In late September, when the state in Belgrade was critical, he led his unit which defended the railway embankment from the "Zlatni šaran" kafana to Knez Mihailova Venac from the incoming Austro-Hungarians.
[3] The detachment was ordered to retreat to the heights south of Belgrade, which was the beginning of the large and organized departure of the army towards southern Serbia, Kosovo, Montenegro and Albania.
[7] After the war, he held high offices in the Military-Technical and Engineering Department of the Army and Navy.