Barker joined the Canadian Mounted Rifles in December of 1914. He spent a year in the trenches before transferring to the Royal Flying Corps in April of 1916. After starting out as a mechanic, he qualified as an observer in August 1916 and shot down his first enemy aircraft from the rear seat of a B.E.2d. Assigned to England in November 1916, he soloed after 55 minutes of dual instruction and received a pilot's certificate in January of 1917.
A month later, he was back in France flying an R.E.8 until wounded by anti-aircraft fire on August 7, 1917. When he recovered, he served as a flight instructor before returning to combat duty in France. In November of 1917, his squadron was reassigned to Italy where Barker's Sopwith Camel became the single most successful fighter aircraft of the war. Logging more than 379 hours of flight time, Barker shot down 46 enemy aircraft before Camel #B6313 was retired from service and dismantled on October 2, 1918.
That month, he assumed command of the air combat school at Hounslow. Deciding he needed to brush up on air combat techniques for his new assignment, Barker joined 201 Squadron for ten days in France. During that time, he saw no action and was about to return to England when he decided to make one more excursion over the front.
On October 27, 1918, while flying alone, he encountered sixty Fokker D.VIIs flying in stepped formation. In this hreoic battle with Jagdgeschwader 3, Barker shot down four enemy aircraft despite serious wounds to both legs and his elbow. Fainting from pain and loss of blood, he managed to crash land his Snipe safely behind British lines. Barker received the Victoria Cross (VC) for this action.
Victoria Cross (VC)
"On the morning of the October 27, 1918, this officer observed an enemy two-seater over the Foret de Mormal. He attacked this machine and after a short burst it broke up in the air. At the same time a Fokker biplane attacked him, and he was wounded in the right thigh, but managed, despite this, to shoot down the enemy aeroplane in flames. He then found himself in the middle of a large formation of Fokkers who attacked him from all directions, and was again severely wounded in the left thigh, but succeeded in driving down two of the enemy in a spin. He lost consciousness after that, and his machine fell out of control. On recovery, he found himself being again attacked heavily by a large formation, and singling out one machine he deliberately charged and drove it down in flames. During this fight his left elbow was shattered and he again fainted, and on regaining consciousness he found himself still being attacked, but notwithstanding that he was now severely wounded in both legs and his left arm shattered, he dived on the nearest machine and shot it down in flames. Being greatly exhausted, he dived out of the fight to regain our lines, but was met by another formation, which attacked and endeavored to cut him off, but after a hard fight he succeeded in breaking up this formation and reached our lines, where he crashed on landing. This combat, in which Major Barker destroyed four enemy machines (three of them in flames), brought his total successes to fifty enemy machines destroyed, and is a notable example of the exceptional bravery and disregard of danger which this very gallant officer has always displayed throughout his distinguished career." VC citation, London Gazette, November 30, 1918
Military Cross (MC)
"For conspicuous gallantry in action. He flew at a height of 500 feet over the enemy's lines, and brought back most valuable information. On another occasion, after driving off two hostile machines, he carried out an excellent photographic reconnaissance." MC citation, London Gazette, January 10, 1917
Military Cross (MC) Bar
"For conspicuous gallantry and devotion to duty. He has done continuous good work in co-operation with the artillery, and has carried out successful reconnaissances under most difficult and dangerous conditions." MC Bar citation, London Gazette, July18, 1917
Military Cross (MC) Bar
"For conspicuous gallantry and devotion to duty. When leading patrols he on one occasion attacked eight hostile machines, himself shooting down two, and on another occasion seven, one of which he shot down. In two months he himself destroyed four enemy machines and drove down one and burned two balloons." MC Bar citation, London Gazette, September 16, 1918
Distinguished Service Order (DSO)
"For conspicuous gallantry and devotion to duty. When on scouting and patrol work he has on five different occasions brought down and destroyed five enemy aeroplanes and two balloons, though on two of these occasions he was attacked by superior numbers. On each occasion the hostile machines were observed to crash to earth, the wreckage bursting into flames. His splendid example of fearlessness and magnificent leadership have been of inestimable value to his squadron." DSO citation, London Gazette, July 18, 1918
Distinguished Service Order (DSO) Bar
"A highly distinguished patrol leader whose courage, resource and determination has set a fine example to those around him. Up to the 20th July, 1918, he had destroyed thirty-three enemy aircraft - twenty-one of these since the date of the last award (second Bar to the Military Cross) was conferred on him. Major Barker has frequently led the formation against greatly superior numbers of the enemy with conspicuous success." DSO Bar citation, London Gazette, November 2, 1918