In 1940, "he enrolled in the
Royal Canadian Army Medical Corps, and in November of that year, he was transferred to the newly formed Royal Canadian Air Force Medical Branch." From 1940 to 1945, Nelson worked "as a Medical Officer at various
RCAF stations in Canada." in Ottawa, Ontario. He "assumed command of the RCAF Institute of Aviation Medicine in Toronto", Ontario in 1957, and four years later, was "posted to London, England and appointed Medical Liaison Officer at the Canadian Joint Staff." In 1964, Nelson was promoted to the rank of Air Commodore, and appointed "Deputy Surgeon General (Professional)." He served in that position for four years until 1968 when he was promoted to Major-General, and appointed Surgeon General. Nelson remained in the position until his retirement from the military in 1970. ==Retirement==