Military Service/ alternative service
Male Austrian citizens above the age of eighteen are subject to compulsory military service. Female Austrian citizens have the possibility to enter voluntary military service. Male citizens have the right to choose between military and alternative service (e.g. with certain NGOs).
Austrian citizens with permanent residence abroad
Male Austrian citizens with permanent residence abroad must register with the Austrian Embassy or Consulate General in or accredited to their country of residence once they reach the age of 17. However, they will not be invited to present themselves to the examination board while living abroad permanently. Once they move their residence to Austria, they are obliged to register with the army headquarters in their province (Bundesland) of residence within three weeks of their arrival. They will then receive an invitation to present themselves to the examination board. More information on the topic can be found here.
Military/alternative service in case of dual or multiple citizenship
In case of voluntary entry into the military service of a foreign state (e.g. Foreign Legion), Austrian citizenship will be revoked even if the person thereby becomes stateless. However, the completion of mandatory military service in a State of which the person liable for military service is also a national does not lead to a loss of nationality - but any voluntary extension, even if only for one day, does.