Rumbold akanyoresa muRoyal New Zealand Naval Volunteer Reserve uye muna 1941 akagamuchirwa nokuda kwokurovedzwa kuva mukuru mukuru muEngland paRoyal Naval College, Greenwich. Paakapedza chikoro akabatana neDestroyer, achishanda somutevedzeri womutevedzeri mumotokari dzeArctic. Muna 1943, akashumira ari mungarava inonzi "Inglefield" panguva yokurwisa Sicily
. Akapona pakanyura ngarava muna February 1944 panguva yeOperation Shingle uye ndiye akanga ari munhu wokupedzisira kusiya ngarava, achibatsira vamwe vashandi kuti vabve, izvo zvaakataurwa mumashoko. Kutevera kunyura, akagadzwa mureza lieutenant kuna Rear-Admiral Gerald Dickens, kushumira naye North Africa, kweBrussels uye The Hague.