Haig attended the Royal Military College, Sandhurst and was commissioned as a second lieutenant on the unattached list for the British Indian Army on 18 January 1905. He was first attached to a British Army regiment in India for a year then appointed to the 24th Punjabis, Indian Army on 19 March 1906. He received promotion to lieutenant on 18 April 1907 and to captain on 18 January 1914. During the First World War he served in Egypt from 18 November 1914 to 22 March 1915 and Mesopotamia from 7 April 1915 to 29 April 1916 when he was taken prisoner at the Fall of Kut. During this time he was wounded, was mentioned in dispatches twice and was awarded the Military Cross and bar. The bar to his Military Cross was for successfully escaping from his Prisoner of war camp in August 1918. This was awarded 10 June 1920.
Return to India
Haig was appointed temporary major on 14 September 1919, at the same time becoming a General Staff Officer until 30 September 1920. He was re-appointed a General Staff Officer on 1 April 1922 for the United Provinces district until 20 February 1923. He was appointed an instructor at the Staff College in Quetta on 21 February 1923 until 9 August 1926 by which time, with the post war reforms the 24th Punjabis were now titled the 4th battalion, 14th Punjab Regiment. He attended the Imperial Defence College in 1929, then was appointed brevet lieut-colonel then promoted to substantive lieutenant-colonel which was confirmed on 10 February 1930. Haig was appointed commanding officer of the 4th Battalion 14th Punjab Regiment 10 February 1930. Haig was appointed a temporary brigadier and substantive colonel on 4 June 1932, upon his appointment as Deputy Director of Staff Duties. He vacated this position on 25 October 1933 and was appointed to command the 7th Dehra Dun Brigade. Haig was appointed Deputy Adjutant and Quartermaster General of the Eastern Command on 28 February 1936, once more retaining the temporary rank of brigadier. Haig received promotion to major-general on 6 June 1936 and ceased to be Deputy Adjutant and Quartermaster General on 27 April 1937. He was appointed a Companion of the Order of the Bath on 1 February 1937. Haig became colonel of the 4th Battalion, 14th Punjab Regiment on 9 July 1937 and the same year was appointed commandant of the Quetta Staff College.
Haig was appointed Quartermaster General of Army Headquarters India and acting lieutenant-general on 16 March 1940. This was confirmed as a substantive rank on 1 April that year. He became a full general on 10 May 1941 and was appointed Adjutant-General of India on 15 May. From October 1941 until June 1942 he was General Officer Commanding in Chief of the Southern Command. He was appointed a Knight Commander of the Order of the Bath on 11 June 1942. He retired on 16 August 1942.
