Mezue ahịrịokwu na - esonụ: N'afọ 1910, a kpọfere Nelles n'Òtù Ndị Agha Mmiri Royal na - amalite amalite, ọ ghọkwara onye na - akwọ ụgbọ mmiri n'ụgbọ mmiri ọhụrụ e wuru na Canada. N'ime afọ iri sochirinụ, ọ ga-ebili site n'ọkwa nke sub-lieutenant ruo n'ọkwa nke onye isi dị ka osote onye isi ndị ọrụ ụgbọ mmiri. N'ihi obere nke RCN, e zigara ndị isi ndị Canada ka ha zụọ ụgbọ mmiri buru ibu nke Royal Navy nke Britain iji nweta ahụmịhe. N'ọnwa Disemba afọ 1911, Nelles sonyere n'ụgbọ agha. Na mbido afọ 1914, a kpọgara Nelles n'ụgbọ mmiri ahụ, nke e kenyere na North America na West Indies Station dabere na Bermuda. Ná mmalite afọ 1914 e zigara "Suffolk" ichebe ọdịmma ndị Britain na Mexico n'oge Agha Ụwa Mbụ.
agha obodo. Mgbe Agha Ụwa Mbụ malitere, e nyere "Suffolk" iwu ka o chebe ụzọ ụgbọ mmiri ndị na-agafe Oké Osimiri Atlantic, ma mesịa na-agagharị n'agbata Bermuda na Halifax, Nova Scotia. Nelles nọgidere n'ụgbọ mmiri ndị Britain ruo n'April 1917, mgbe a kpọghachiri ya na Ottawa, Ontario. N'ebe ahụ, o jere ozi dị ka onye isi ọkọlọtọ na onye isi mbụ nke RCN, Admiral Sir Charles Kingsmill. N'afọ 1920, Nelles banyere na Royal Naval College, e buliri ya n'ọkwa lieutenant commander n'afọ 1922 ma jee ozi n'ọtụtụ ụlọ ọrụ Royal Navy n'ime afọ abụọ sochirinụ tupu ọ laghachi na Canada na 1925.