He entered National Service in 1950, was commissioned in the Royal Army Service Corps (RASC), and served as a Motor Transport Officer in the Suez Canal Zone and Aqaba, Jordan.

Middlebrook wrote his first book The First Day on the Somme (1971) following a visit to the First World War battlefields of France and Belgium in 1967.

[1] The book is a detailed study of the single worst day for the British Army.

Middlebrook gave the same single-day treatment to 21 March 1918, the opening of the German spring offensive, in The Kaiser's Battle.

[citation needed] Middlebrook died in Cheltenham on 19 January 2024, at the age of 91.