Gerke was born in Claremont, Western Australia on 7 June 1916.
During the Second World War he enlisted in the Second Australian Imperial Force (2nd AIF) on 6 August 1940.
[2] Placed into the Reserve of Officers in 1947, he was promoted to captain in 1950 and served in the 3rd Battalion, Royal Australian Regiment (3 RAR) during the Korean War in 1951–52.
[2] He was awarded the Distinguished Service Order for bravery and leadership during the Battle of Maryang San in July 1951.
[2] In 1976 he was appointed a Member of the Order of Australia for service to veterans.