Arnold enlisted on 5 Apr 1941 and was posted to Australian Army Service Corps, Sparrow Force on 29 Jul 1941.
Arnold joined the unit on Timor as a Private from Australian Army Service Corps, after the fall of Koepang, approx March 1942. Late in Mar 1942, he was part of Lt Doig's No 13 Section, comprising men, from the Koepang end of Timor, that were stationed at Maliana to patrol the boarder area. He later attended a special training course at “Sinaro” and served as a Tommy Gunner with Lt Rodd and Lt Green’s Sect’s.
After the campaign on Timor, he embarked with the unit, for Australia aboard the Royal Dutch destroyer “Tjerk Hiddes” on 11 Dec 1942.
He left the unit on and was posted to 6th Advanced Workshops, Royal Australian Engineers on 24 Mar 1943. He transferred to 4th Australian Infantry Workshop on 24 Jun 1943 and embarked with them for New Britain aboard "DUNTROON" on 25 Aug 1944. He was appointed paid Lance Corporal on 6 Dec 1944. He flew from HOLLANDIA to MEDANG, New Guinea on 8 Mar 1945 and embarked for MOROTAI aboard "GORGON" on 17 Mar 1945, transferring to 2/11th Field Company on 21 Apr 1945. He suffered very serious burns on 5 May 1945 and was Medevac to Australia, aboard "MANUNDA" on 16 Jun 1945 and after treatment, he was discharged on 20 Nov 1945.
He was entitled to the 1939-45 Star, Pacific Star, War Medal and Australian Service Medal 1939-45, pictured below.