Corbett enlisted in the Royal Marines during the Second World War, and served in the Home Fleet on the heavy cruiser HMS "Devonshire". After VJ Day in 1945, he was posted to the Far East, where he was involved in quelling unrest in New Guinea and reportedly killed two Japanese soldiers there whilst engaged in hand-to-hand fighting. He was then posted to Tonga, but deserted and remained in Australia before handing himself in to the Military Police. His military service left him with a damaged bladder following an infection, and a red mark on his eye caused by a thorn, which was not treated until late in his life.