[4] Hagenauer set up a medical practice in Traralgon and married Margaret Hay, a local nurse, who died in 1914.
[4] Their son Frederick would die in World War II while serving as a 2nd Lt with 1st Battalion, Scottish Royal Highlanders on 13 October 1940.
[4] On 24 September 1915 Hagenauer enlisted (as the anglicised "Henry Alexander Hagen") in the Australian Army Medical Corps, attaining the rank of Major.
[6] Posted to 2nd Anzac Headquarters in France as a Regimental Medical Officer, Hagenauer was invalided to England in January 1917.
[4] He was then attached to No 1 Convalescent Depot till September 1918, before being transferred to No 1 Australian Dermatological Hospital.