Born in Java (Dutch East Indies), Johannes Walter served in the Navy from 1st January 1942, until he arrived in England on 3rd May. He was detached from the Navy, and sent on wireless training with the RAF in Blackpool, and then based with 320 Sqdn. Around June 1943, he was approached by the SOE which wanted him as a wireless operator; he was discharged from the Navy on 12th June 1944.

Whilst in England he married an English girl, Margaret. When he left for his mission to Holland, he was expecting their child.