Promoted to lieutenant on 6 August 1890,[3] Chetwode first saw active service in the Chin Hills expedition in Burma from 1892 to 1893[2] and was promoted to captain on 7 February 1897.[4] 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.[5] Promoted to major on 21 December 1901,[6] he stayed in South Africa until the end of hostilities. 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.[7] He succeeded as 7th Baronet in 1905.[2]
In 1906, Chetwode became assistant military secretary to Sir John French and on 3 January 1908 he was promoted to lieutenant colonel[8] on appointment as commanding officer of the 19th Hussars.[2] Having been placed on half-pay list from 3 January 1912,[9] he was promoted to colonel on 1 April 1912[10] and appointed Commander of the London Mounted Brigade.[2]
During the Curragh incident in March 1914 Chetwode was offered command of the 3rd Cavalry Brigade when Hubert Gough threatened to resign.[2] He knew that he would be "looked upon by all his brother officers as a scab” but thought it "his duty as a soldier to do as he was ordered & not to meddle in politics".[11] In the event Gough kept his command and Chetwode remained with the London Mounted Brigade, but his willingness to replace Gough caused some ill feeling.[2] Promoted to temporary brigadier-general on 15 May 1914,[12] he was given command of the 5th Cavalry Brigade in August 1914.[2]
Chetwode became Chief of the General Staff in India in 1928 and Commander-in-Chief, India, in November 1930.[16] He was promoted to field marshal on 13 February 1933.[20] In his tenure as Commander-in-Chief, India, Chetwode was an opponent of replacing horses with tanks; he "made the surprising pronouncement that the Army in India would be unlikely to adopt tanks for a very long time, and then only to keep up the momentum of horsed cavalry."[21] He was much concerned with the modernisation and "Indianisation" of the army in India. The main building and its central hall at the Indian Military Academy is named after him. The credo of the academy, engraved on the entrance to the central hall, is a passage from his address delivered at the formal inauguration of the academy in 1932:
The safety, honour and welfare of your country come first, always and every time.
The honour, welfare and comfort of the men you command come next.
Your own ease, comfort and safety come last, always and every time.
This is known as the "Chetwode Motto" and is the motto of the officers passing out from the academy.[22]
Chetwode married Hester (Star) Alice Camilla Stapleton Cotton and had a son Roger and a daughter Penelope.[23]
Roger Chetwode married Honourable Molly Berry, daughter of the 1st Viscount Camrose. He was killed on active service on 14 August 1940 at age 34, leaving two sons: Philip, the 2nd Baron Chetwode, and Christopher.