Born the son of Sir George Chetwode, 6th Baronet, and Alice Jane Bass (daughter of Michael Thomas Bass the brewer), Chetwode was educated at Eton, where he was an athlete of some distinction, and entered the British Army through the Militia with his first commission being as a second lieutenant in the 3rd (Militia) Battalion of the Oxfordshire Light Infantry (later the Oxfordshire and Buckinghamshire Light Infantry) on 11 April 1888.

[5] He served in the Second Boer War where he took part in the actions at Reitfontein in October 1899, Ladysmith in December 1899, Laing's Nek in June 1900 and Belfast in August 1900: he was twice mentioned in despatches and was awarded the Distinguished Service Order.

The war ended with the Peace of Vereeniging in late May 1902, and the following month Chetwode returned home in the SS Tagus, arriving at Southampton in July.

[11] On 1 April he reverted to normal pay and succeeded Colonel Thomas Calley as commander of the London Mounted Brigade, a Territorial Force (TF) formation.

[4][12] During the Curragh incident in March 1914 Chetwode was offered command of the 3rd Cavalry Brigade when Brigadier General Hubert Gough threatened to resign.

[4] Promoted to the temporary rank of brigadier general on 15 May,[14] he was given command of the 5th Cavalry Brigade in August 1914, the same month of the British entry into World War I.

[4] During the war, Chetwode served on the Western Front: his 5th Cavalry Brigade helped cover the retreat from the frontier, and checked the pursuing Germans at Cerizy on 29 August 1914.

[16] With the war on the Western Front bogged down in trench warfare, Chetwode was lucky to be transferred to Palestine where he was given command of the Desert Column and promoted to temporary lieutenant general with effect from 22 November 1916.