Flight Lieutenant Arthur Frederick Blackwell enlisted to the Royal Australian Air Force on 31 March 1941. Mustering as a Navigator and given the service number of 403980, Blackwell conducted initial training in Australia, before travelling to Canada and the United Kingdom to undertake further advanced navigational training. After passing training he was promoted to sergeant and posted to the United Kingdom-based No. 500 Squadron, Royal Air Force (RAF) in July 1942. This unit flew as part of the RAF Coastal Command on anti-submarine, convoy escort and patrolling missions. No. 500 Squadron was deployed to Gibraltar in November 1942 to patrol the vital approaches to the Mediterranean. A detachment of the squadron was forward-deployed to Tafaraoui airfield in Oman to provide further protection for Allied convoys and to detect and sink any enemy submarines.
In April 1943, Blackwell was the navigator of a Lockheed Hudson conducting a night-time anti-submarine patrol in the western Mediterranean. Using airborne radar installed on the aircraft, the crew detected a German U-boat and proceeded to attack it from low altitude. As the aircraft passed very close to the submarine a burst of anti-aircraft cannon fire from the submarine hit the cockpit, instantly killing the pilot and damaging the aircraft.
Quickly working with other members of the crew, Blackwell removed the pilot from the seat whilst maintaining control of the aircraft. He then occupied the pilot seat and safely flew the damaged aircraft back to base. Once over the airfield the remaining aircrew successfully bailed out of the Hudson. Blackwell then successfully belly landed the Hudson near the airfield.
For his actions that night, and his display of "exceptional leadership and captaincy which inspired his comrades in trying circumstances", Blackwell was immediately awarded the Conspicuous Gallantry Medal (CGM). Second only to the Victoria Cross for naval and air personnel, his was the first CGM awarded to a member of the Royal Australian Air Force.
After flying 443 combat hours with No. 500 Squadron, his active tour with the unit ended in August 1943. Blackwell returned to the United Kingdom for several instructional postings, where he was promoted to flying officer in December 1943. In March 1945 Blackwell was presented his CGM by King George VI at Buckingham Palace. Later in June 1945 he was promoted to flight lieutenant before returning to Australia the following month to begin his demobilisation. Flight Lieutenant Blackwell was discharged on 22 October 1945.