austrian-hungarian military:
http://www.kuk-wehrmacht.de/regiment/index.html

WW1: http://en.wikipedia.org/wiki/World_War_I

but your ancestors can have been also from the Kingdom of Serbia. only area north of Belgrad was that time austrian-hungarian.
http://www.kuk-wehrmacht.de/regiment/img/oegarnkart1898.jpg

"There are numerous Serbs who migrated to Indiana from that part of Serbia that was occupied by the Turks in those days."
no Turks longer that time there!
info:
http://en.wikipedia.org/wiki/Kingdom_of_Serbia#Principality_...
http://en.wikipedia.org/wiki/Kingdom_of_Serbia#Balkan_Wars_a...
http://de.wikipedia.org/w/index.php?title=Datei:Serbia1913.p...

Loss of territory of the Ottoman Empire
http://de.wikipedia.org/w/index.php?title=Datei:Naher_Osten_...