Question: When did the military branch Charles Burnett served in start to wear khaki?

full_context: Document 1: Gerald Cuthbert: Major-General Gerald James Cuthbert (12 September 1861 – 1 February 1931) was a British Army officer who commanded a battalion in the Boer War and a division in the First World War. Cuthbert joined the Scots Guards in 1882 and served in Egypt and the Sudan during the late 19th century. During the Boer War he served with his regiment, rising to command a battalion and after the war he was given command of a brigade in the Territorial Force and then in the British Expeditionary Force of 1914. He served on the Western Front from 1914 to 1917, rising to command 39th Division, then returned to home service before retiring in 1919.
Document 2: Navy blue: Navy blue got its name from the dark blue (contrasted with white) worn by officers in the British Royal Navy since 1748 and subsequently adopted by other navies around the world. When this color name, taken from the usual color of the uniforms of sailors, originally came into use in the early 19th century, it was initially called "marine blue", but the name of the color soon changed to "navy blue".
Document 3: Airman Battle Uniform: On 2 October 2007, the Air Force began issuing the ABU to enlisted trainees in Basic Military Training at Lackland AFB and was issued to the Class of 2012 at the United States Air Force Academy on 26 June 2008, and is now available for purchase by all Airmen. Since 2008, it has been issued to Airmen deploying to locations in CENTCOM, including Kuwait, Iraq and Afghanistan. Personnel in other countries were issued DCU uniforms while inventory lasted. The ABU is available at Army and Air Force Exchange Service (AAFES) military clothing stores. Although the Air Force has officially recognized color variations in different set of ABUs, all variations are currently authorized to wear and the problem should be fixed when the patterns are finalized within a year.
Document 4: Uniforms of the United States Navy: The Navy first authorized a khaki uniform in 1913 as a practical garment for early naval aviators; they were given permission to wear Marine Corps khaki uniforms with naval insignia, when flying or working on aircraft. Khakis were authorized aboard submarines in 1931 and as a working uniform on all ships ten years later.
Document 5: Charles Henry Adair: Admiral Charles Henry Adair (2 July 1851 – 9 March 1920) was a Royal Navy officer in mid-late 19th century and the early 20th century. He retired just prior to the outbreak of World War I.
Document 6: Charles Foulkes (British Army officer): Major-General Charles Howard Foulkes CB CMG DSO (1 February 1875 – 6 May 1969) was a Royal Engineers officer in the British Army and also a British international field hockey player who competed in the 1908 Summer Olympics in the bronze medal-winning team. He saw service in World War I and, following the first German use of gas on 22 April 1915 at the Second Battle of Ypres, became Britain's chief advisor on gas warfare. He also advised on the use of gas to suppress the uprisings in Afghanistan (1919) and Waziristan (1920), but gas was never actually deployed in these conflicts.
Document 7: Charles Burnett (British Army officer): General Sir Charles John Burnett (30 October 1843 – 10 November 1915) was a British Army officer at the end of the nineteenth century and during the early years of the twentieth century.
Document 8: British Army during the Second World War: The pre-war British Army was trained and equipped to be a small, mechanised, professional army. Its main function was to garrison the British Empire. It became evident early in the war that its initial structure and manpower was woefully unprepared and ill - equipped for a war with multiple enemies on multiple fronts. The British Army, an all - volunteer force until 1939, was small in comparison to its enemies at the start of the Second World War in 1939, as it had been in the First World War. By the end of the Second World War, however, over 3.5 million men had served in the British Army.
Document 9: Service Dress (British Army): Service Dress was the new style of khaki service dress uniform introduced by the British Army for use in the field from the early 1900s, following the experiences of a number of imperial wars and conflicts, including the Second Boer War. This variant of uniform continues to be worn today, although only in a formal role, as No. 2 Pattern dress.
Document 10: Charles Griffin: Charles Griffin (December 18, 1825 – September 15, 1867) was a career officer in the United States Army and a Union general in the American Civil War. He rose to command a corps in the Army of the Potomac and fought in many of the key campaigns in the Eastern Theater.
Document 11: Charles Young (United States Army): Charles Young (March 12, 1864 -- January 8, 1922) was the third African - American graduate of West Point, the first black U.S. national park superintendent, first black military attaché, first black man to achieve the rank of colonel, and highest - ranking black officer in the Regular Army until his death in 1922.
Document 12: Eton College: The long-standing claim that the present uniform was first worn as mourning for the death of George III is unfounded. "Eton dress" has undergone significant changes since its standardisation in the 19th century. Originally (along with a top-hat and walking-cane), Etonian dress was reserved for formal occasions, but boys wear it today for classes, which are referred to as "divisions", or "divs". As stated above, King's Scholars wear a black gown over the top of their tailcoats, and occasionally a surplice in Chapel. Members of the teaching staff (known as Beaks) are required to wear a form of school dress when teaching.
Document 13: United States Air Force: The first USAF dress uniform, in 1947, was dubbed and patented "Uxbridge Blue" after "Uxbridge 1683 Blue", developed at the former Bachman-Uxbridge Worsted Company. The current Service Dress Uniform, which was adopted in 1993 and standardized in 1995, consists of a three-button, pocketless coat, similar to that of a men's "sport jacket" (with silver "U.S." pins on the lapels, with a silver ring surrounding on those of enlisted members), matching trousers, and either a service cap or flight cap, all in Shade 1620, "Air Force Blue" (a darker purplish-blue). This is worn with a light blue shirt (Shade 1550) and Shade 1620 herringbone patterned necktie. Enlisted members wear sleeve insignia on both the jacket and shirt, while officers wear metal rank insignia pinned onto the coat, and Air Force Blue slide-on epaulet loops on the shirt. USAF personnel assigned to Base Honor Guard duties wear, for certain occasions, a modified version of the standard service dress uniform, but with silver trim on the sleeves and trousers, with the addition of a ceremonial belt (if necessary), wheel cap with silver trim and Hap Arnold Device, and a silver aiguillette placed on the left shoulder seam and all devices and accoutrement.
Document 14: Charles Edward Callwell: Major-General Sir Charles Edward Callwell (2 April 1859 – May 1928), was an Anglo-Irish officer of the British Army, who served in the artillery, as an intelligence officer, and as a staff officer and commander during the Second Boer War, and as Director of Operations & Intelligence during World War I. He was also a noted writer of military biography, history, and theory.
Document 15: Red coat (military uniform): Red coat or Redcoat is a historical item of military clothing used widely, though not exclusively worn, by most regiments of the British Army from the 17th to the 20th centuries. From the mid-17th century to the 19th century, the uniform of most British soldiers (apart from artillery, rifles and light cavalry) included a madder red coat or coatee. From 1873 onwards, the more vivid shade of scarlet was adopted for all ranks, having previously been worn only by officers, sergeants and all ranks of some cavalry regiments.
ground_truth: early 1900s
sub_queries: Charles Burnett >> military branch Answer: British Army
when did British Army start wearing khaki Answer: early 1900s