Question: When did the army that introduced tanks to battlefields in WWI start wearing khaki?

full_context: Document 1: 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 2: Covenanter tank: The Cruiser tank Mk V or A13 Mk III Covenanter was a British cruiser tank of the Second World War. The Covenanter was the first cruiser tank design to be given a name. Designed by the London, Midland and Scottish Railway as a better-armoured replacement for the Cruiser Mark IV, it was ordered into production in 1939 before pilot models were built. Problems with the design became apparent only after production was under way.
Document 3: 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 4: Tanks in World War I: The development of tanks in World War I was a response to the stalemate that had developed on the Western Front. Although vehicles that incorporated the basic principles of the tank (armour, firepower, and all - terrain mobility) had been projected in the decade or so before the War, it was the alarmingly heavy casualties of the start of its trench warfare that stimulated development. Research took place in both Great Britain and France, with Germany only belatedly following the Allies' lead.
Document 5: 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.
Document 6: 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 7: 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 8: 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 9: Tanks in World War I: In Great Britain, an initial vehicle, nicknamed Little Willie, was constructed at William Foster & Co., during August and September 1915. The prototype of a new design that became the Mark I tank was demonstrated to the British Army on February 2 1916. Although initially termed ``Landships ''by the Landship Committee, production vehicles were named`` tanks'', to preserve secrecy. The term was chosen when it became known that the factory workers at William Foster referred to the first prototype as ``the tank ''because of its resemblance to a steel water tank.
Document 10: VT tank: The first VT tank, VT 1-1, was built in 1974 by Maschinenbau Kiel (MaK). One year later they produced the second VT tank, the VT 1-2. For further testing of the mobility and the concept of a tank with two main guns, five Gefechtsfeldversuchträger (GVT, "battlefield test-beds") were designed and built in 1975 and 1976.
Document 11: Levavasseur project: The Levavasseur project was an early project for a tank designed in 1903 by the French Captain Léon René Levavasseur (1860-1942) of the 6th Artillery Battalion, described as a "self propelled cannon project" (French: "Projet de canon autopropulseur"). It is considered as the first description, made by a soldier, of what would come to be known as the tank. Levavasseur was a graduate of Ecole Polytechnique, of the promotion of 1881. According to "Armoured Fighting Vehicles of the World":
Document 12: Mark IV tank: The Mark IV was built by six manufacturers: Metropolitan (the majority builder), Fosters of Lincoln, Armstrong-Whitworth, Coventry Ordnance Works, William Beardmore and Company and Mirrlees, Watson & Co., with the main production being in 1917. The first order was placed for 1,000 tanks with Metropolitan in August 1916. It was then cancelled, reinstated and then modified between August and December 1916. The other manufacturers, contracted for no more than 100 tanks each, were largely immune to the conflict between Stern and the War Office.
Document 13: Valentine tank: The Tank, Infantry, Mk III, Valentine was an infantry tank produced in the United Kingdom during the Second World War. More than 8,000 of the type were produced in eleven marks, plus various specialised variants, accounting for approximately a quarter of wartime British tank production. The many variants included riveted and welded construction, petrol and diesel engines and a progressive increase in armament. It was supplied in large numbers to the USSR and built under licence in Canada. Developed by Vickers, it proved to be both strong and reliable.
Document 14: 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 15: 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.
ground_truth: early 1900s
sub_queries: the tank was introduced by to the battlefields of world war i by Answer: the British Army
when did the British Army start wearing khaki Answer: early 1900s