Enlisted into the 2nd Pretoria Regiment and served with them from February to September, 1940, and as Lance Bombardier with 93 Field Battery, Rand U.T.C., from February to November 1942, when he transferred to the S.A.N.F. He was seconded to the Royal Navy in February 1943 and saw active service as a Sub-Lieutenant, and later as a full Lieutenant, in Pacific, Italian and Mediterranean waters throughout the war. He was appointed Lieutenant, Royal Navy, in September 1949 and continued to serve until his accidental death in England in 1951. His medals 1939-45 Star; Italy Star; Pacific Star; War Medal; Africa Service Medal, all officially named (587005 J. D. Trewartha) together with photograph, original typed record of service, letter of appointment as Lieut. R.N. and named medal entitlement slip sold at Dix Noonan Webb for 75 pounds 22nd June 1999
LG Sup 17 April 1917 - "For conspicuous gallantry and devotion to duty. He displayed great courage on several occasions in getting his men and mules through heavy shell fire. He set a splendid example to his men throughout under the most difficult circumstances."