The fifth son of William Cuthbert of Beaufront Castle in Northumberland, Gerald was privately educated, and attended the Royal Military College at Sandhurst.

In April 1889, after being seconded for service on the staff,[8] he was made an aide-de-camp to Major General Frederick Forestier-Walker at Aldershot,[3][9] an assignment he held until 1890.

He was mentioned in dispatches during the war, and given a brevet promotion to lieutenant colonel (dated 29 November 1900) in the South Africa Honours list 1901.

[7][18] Later that year, after being removed off half-pay, he was posted to Egypt as a temporary assistant adjutant-general (AAG); this was made permanent in December, when he was promoted to substantive colonel.

[5] After the First World War began in August 1914, Cuthbert remained in command of 13th Brigade when it was mobilised for service in the British Expeditionary Force.

[25] He remained with them through 1915 and 1916, culminating in the German attack on Vimy Ridge in May 1916, where Cuthbert led the division in lieu of the divisional commander, who was on leave.

[26][27] He was not a popular brigadier; the London volunteers particularly objected to his strict views on cleanliness, a story circulated that he had ordered front-line trenches to be swept out with brooms.

[30] His record with the division was not well received by his superiors; Lieutenant General Claud Jacob of II Corps described him as "obstinate and mulish" during the Battle of the Somme, whilst Lieutenant General Ivor Maxse of XVIII Corps noted he had "little or no conception of training methods", and "few ideas" regarding tactical operations; his only merit was perceived to be his rigorous approach to discipline.