paragraph_text: It was used extensively by the armed forces of United Kingdom during the Second World War as a mounted machine gun for tanks and other armoured vehicles as a replacement for the heavier, water-cooled Vickers machine gun. Although it required a rather large opening in the tank's armour, it was reliable.

paragraph_text: The Kliment Voroshilov (KV) tanks, a series of Soviet heavy tanks named after the Soviet defence commissar and politician Kliment Voroshilov, operated with the Red Army during World War II. The KV tanks were known for their heavy armour protection during the early stages of the war, especially during the first year of the German invasion of the Soviet Union. In certain situations, even a single KV-1 or KV-2 supported by infantry could halt large German formations. The German Wehrmacht at that time rarely deployed its tanks against KVs, as their own armament was too poor to deal with the ""Russischer Koloss"" – "Russian Colossus".

paragraph_text: 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.

paragraph_text: The Ordnance QF 20 pounder (known as 20 pounder, 20 pdr or simply 20-pr) was a British 84 mm (3.307 inch) tank gun. It was introduced in 1948 and used in the Centurion main battle tank, Charioteer medium tank, and Caernarvon Mark II heavy tank. The 20 pounder was designed to replace the effective Ordnance QF 17 pounder, which had proven itself in World War II. However, once the gun was found to have inadequate performance against the Soviet T-54, the gun was mostly replaced in service by the larger calibre 105 mm L7 gun.

paragraph_text: 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.

paragraph_text: The Ampulomet (, also rendered "Ampulomyot", "ampulla mortar", etc., lit. "ampule/vial thrower" cf. миномёт) was an expedient anti-tank weapon which launched a 125 mm incendiary projectile made of spherical glass. This weapon was introduced in 1941 and used (to a limited degree) by the Red Army in World War II, but by 1942 was largely obsolete.

paragraph_text: The M19 Tank Transporter (US supply catalog designation G159) was a heavy tank transporter system used in World War II and into the 1950s. It consisted of a 12-ton 6x4 M20 Diamond T Model 980 truck and companion 12-wheel M9 trailer.

paragraph_text: The Battle of Hannut was a Second World War battle fought during the Battle of Belgium which took place between 12 and 14 May 1940 at Hannut in Belgium. It was the largest tank battle in the campaign. It was also the largest clash of tanks in armoured warfare history at the time.

paragraph_text: 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.

paragraph_text: The .55 Boys was adopted and manufactured alongside the Boys Anti-Tank Rifle in 1937 throughout the Commonwealth of Nations by firms such as Kynoch. However, when the United Kingdom entered World War II, the .55 Boys round was soon found to be insufficient against even early war Axis tanks in late 1939 and 1940. However, the United Kingdom had to rely on the .55 Boys round for several years because no better infantry anti-tank weapons were available. When the PIAT anti-tank weapon was introduced in 1943, the shaped charges it fired proved to be far more effective against enemy armor than the .55 Boys round had The Boys rifle was phased out of service as the PIAT became the British military's primary handheld anti-tank weapon. Despite its lack of effectiveness as an anti-tank weapon, the .55 Boys was used throughout World War II in both the Pacific and Atlantic theaters and also saw use during the Winter War and Continuation War by Finland. By the conclusion of World War II, the .55 Boys was no longer used in any major capacity.

paragraph_text: The Fiat 3000 was the first tank to be produced in series in Italy. It became the standard tank of the emerging Italian armored units after World War I. The 3000 was based on the French Renault FT.

paragraph_text: The T-43 medium tank was a prototype Soviet medium tank developed during the Second World War as a possible replacement for both the T-34 medium and KV-1 heavy tanks. The project's aim was to build a medium tank with heavier armour, but German advances in tank technology proved better countered by a more heavily armed T-34-85 and the T-43 was cancelled.

paragraph_text: The Panzer II was designed before the experience of the Spanish Civil War of 1936–39 showed that protection against armour-piercing shells was required for tanks to survive on a modern battlefield. Prior to that, armour was designed to stop machine gun fire and high-explosive shell fragments.

paragraph_text: He served in the German Wehrmacht in World War II as a tank commander, before being wounded in 1942 and evacuated back to Germany.

paragraph_text: 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.

paragraph_text: The Infantry Tank Mark II, best known as the Matilda, was a British infantry tank of the Second World War.

paragraph_text: 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.

paragraph_text: Joe Ekins (15 July 1923 – 1 February 2012) was a World War II British Army veteran. He gained recognition for his action as a tank gunner in France in which he destroyed four tanks in a day, including three Tigers (Tiger tanks numbers 312, 009 & 314).

paragraph_text: The Spanish Civil War, fought between 1936–39, provided an opportunity for many European countries to evaluate new technologies and tactics, including armored warfare. At the beginning of the war, the Nationalist and Popular Fronts each possessed only five World War I-era-design Renault FT light tanks, although these were soon reinforced with imported materiel. Italy began supplying Nationalist Spain with L3/35 tankettes in August 1936. The Soviet Union soon followed suit by supplying the Popular Front with T-26 light tanks in October 1936. Germany sent its first shipments of Panzer I light tanks to the Nationalist Front in September 1936. During the war, France and Poland provided the Popular Front with a number of additional FT light tanks. A considerable number of tanks delivered to the Popular Front were subsequently captured; many of these were put into service against their former owners.

paragraph_text: The ZB-53 was designed by Václav Holek and Miroslav Rolčík of the Zbrojovka Brno works as a replacement for the Schwarzlose machine gun of World War I origin. Based on the earlier vz. 35 machine gun, the prototype was tested in 1936 and the following year the new machine gun was adopted by the Czechoslovak Army with the designation TK vz. 37 ("Heavy Machine Gun Mark 1937"). It was introduced as the standard machine gun of Czechoslovak LT-35 and LT-38 tanks. Czechoslovakia exported the gun to Romania, Yugoslavia, Argentina, Afghanistan, Iran and China (large numbers used during the Second Sino-Japanese War), while UK bought a license and started to produce its own version, known as the Besa machine gun (over 60,000 pieces made). During the German occupation of the factory, large numbers were produced for the Waffen-SS until 1942.

Question: When did the army that introduced tanks to battlefields in WWI start wearing khaki?
Answer: early 1900s