Military career
FitzGeorge followed in his father's footsteps by serving in the British Army. He attended the Royal Military College, Sandhurst and was gazetted in December 1864 as an ensign into the 37th (North Hampshire) Regiment of Foot. On 24 January 1865, FitzGeorge transferred from the 37th Regiment of Foot to become ensign in the Rifle Brigade. While serving in the Rifle Brigade, he was stationed in Montreal with the 1st Battalion for five years, from 1865 to 1870. On 14 July 1869, he was promoted to a lieutenant in the Rifle Brigade.
In 1870, FitzGeorge was appointed aide-de-camp to General Robert Napier, 1st Baron Napier of Magdala, Commander-in-Chief of India and served in this position from 1870 until 1875. While in India, he was part of the suite that accompanied Albert Edward, Prince of Wales (later King Edward VII) during his visit there from September 1875 until May 1876.
FitzGeorge was promoted to captain in the Rifle Brigade in November 1877, and on 20 March 1878, he transferred as a captain to the 11th Hussars, which were then stationed at Colchester Garrison. He served with the 11th Hussars at Aldershot Garrison, Cavalry Barracks, Hounslow, and Birmingham. While FitzGeorge was stationed at Aldershot, his regiment was ordered to embark for service at the Cape of Good Hope following the outbreak of the First Boer War. However, this order was cancelled soon after, and he missed his first and only opportunity for active service. In July 1881, FitzGeorge was promoted to major in the 11th Hussars. He became extra aide-de-camp to Lieutenant-General Sir Archibald Alison, 2nd Baronet, who was in command of troops at Aldershot Garrison on 1 December 1883. FitzGeorge served Alison for two years. In May 1886, he was promoted to lieutenant colonel in the 11th Hussars. The Duke of Cambridge appointed FitzGeorge to serve as his equerry-in-waiting and private secretary on 11 August 1886. In 1888, he attained the military rank of brevet colonel in the 11th Hussars.
While his father continued to reside officially at Gloucester House, his mother lived at nearby 6 Queen Street, which FitzGeorge inherited, along with all of its furniture, following her death in 1890. By 1895, he had moved into Gloucester House to live with his father and manage his affairs. When the Duke of Cambridge relinquished his role as Commander-in-Chief of the Forces on 1 November 1895, FitzGeorge was reverted to half-pay, as he was no longer private secretary to the commander-in-chief position. However, he continued to serve as his father's private secretary and equerry. FitzGeorge retired from the military on 1 November 1900.
As equerry to the Duke of Cambridge, FitzGeorge accompanied his father as an attendant to significant British royal engagements, including: the funeral of his grandmother, Augusta, Duchess of Cambridge, on 13 April 1889; the wedding of his cousin Princess Mary of Teck and Prince George, Duke of York, at Chapel Royal, St James's Palace, on 6 July 1893; the funeral of his aunt, Princess Mary Adelaide, Duchess of Teck, at St George's Chapel, Windsor Castle, on 3 November 1897; and the funeral and funeral procession for his uncle Francis, Duke of Teck, at St George's Chapel, Windsor, on 27 January 1900.
His father served as the head of the British Army as Commander-in-Chief of the Forces from 1856 to 1895, spanning most of FitzGeorge's military career. Regarding his career in the British Army, FitzGeorge remarked, "Throughout my life, I found my parentage rather a hindrance than a help." He said that his father was so concerned with being accused of favouritism that when FitzGeorge was up for an appointment against another officer, the other officer received the appointment. Following his many travels throughout his military career, FitzGeorge claimed to have hunted every type of big-game in the world.