He joined the Royal Flying Corps in 1916 and became a fighter ace in the Middle Eastern theatre, where he was awarded the Military Cross and the Distinguished Service Order and Bar.

Between the wars, Drummond saw action in the Sudan—earning appointment as an Officer of the Order of the British Empire—and was posted to Australia on secondment to the Royal Australian Air Force (RAAF) as Director of Operations and Intelligence.

[1] At 5 ft 7in (171 cm) in height, Drummond was judged too slight of build for the infantry and was instead assigned to the 2nd Stationary Hospital of the Australian Army Medical Corps as an orderly.

[1] Following pilot training in the United Kingdom, Drummond received the rank of temporary second lieutenant and was posted to Egypt, where he was assigned to No.

The Turks were retreating all the time and we had great sport coming down to about 50 feet and peppering them with machine guns ..."[5] On 20 March 1917, Drummond, flying a Royal Aircraft Factory B.E.2, was one of two pilots who strafed enemy troops threatening Lieutenant Frank McNamara as he rescued a downed Australian airman, the action for which McNamara was awarded his Victoria Cross.

[1][12] On 12 December, he and his observer were escorting two Australian aircraft in a Bristol Fighter near Tul Karem, Palestine, when they were spotted by three German Albatros scouts.

[25] He was based in the Sudan from January to July 1920,[26] as part of Britain's system of "control without occupation", using aircraft instead of armies to put down local rebellions.

[27] Returning to Britain, he was appointed an Officer of the Order of the British Empire on 22 July 1921 in recognition of his "excellent work" in the face of "adverse conditions", conducting a successful reconnaissance and bombing campaign against Garjak Nuer tribesmen.

[41] In early 1940 he became involved in preparations for Operation Pike, an Anglo-French plan to bomb oil fields in the Caucasus; the Soviet Union was at this time seen as allied to Nazi Germany, in the wake of the invasion of Poland and the Winter War.

[47] Drummond considered the Middle East a "Battle for Airfields", as whichever side held the Mediterranean landing grounds could protect its shipping at the expense of the enemy's.

[49] Drummond was appointed a Companion of the Order of the Bath on 24 September 1941 "in recognition of distinguished services rendered in operational commands of the Royal Air Force" from 1 October 1940 to 31 March 1941.

[52][53] Australia's High Commissioner to the United Kingdom, Stanley Bruce, had recommended Drummond in a cable to Prime Minister John Curtin on 5 February.

An ongoing conflict between Jones (now promoted air vice-marshal) and Bostock led to moves in April 1943 to bring in an officer senior to both men to head the RAAF in a unified command structure, and Drummond was once more approached by the Australian government.

[58] He was raised to temporary air marshal on 1 June 1943, and appointed a Knight Commander of the Order of the Bath in the King's Birthday Honours the following day.

[1] He remained an advocate of close cooperation between the RAF and Dominion air forces; the Adelaide Advertiser quoted him as saying, "Daily journeying to my London office ...

I make a point of passing the Boomerang Club at Australia House just for the pleasure and gratification of swapping a salute and a 'good day' with some of the best air crew in the world—the RAAF.

"[61] On 27 March 1945, Drummond was en route to Canada with other dignitaries to attend a ceremony marking the closure of the Empire Air Training Scheme.

[1][62] Frank McNamara, now an RAAF air vice-marshal based in England and a close friend, broke the news to Drummond's widow.

[65][66] Drummond was twice mentioned in despatches for his service in World War II, on 11 June 1942,[67] and on 19 September 1946 (for his performance as SASO RAF Middle East in 1940–41).