The Ordnance QF 3 pounder gun was a 47 mm British tank gun based on the Ordnance QF 3 pounder Vickers naval gun, mounted on Vickers Medium Tanks in the 1920s and 1930s.
 The gun was produced in 32 calibre (59 inch) and 40 calibre (74 inch) versions.
The Ordnance Quick-Firing 17-pounder (or just 17-pdr) was a 76.2 mm (3 inch) gun developed by the United Kingdom during World War II.
 It was used as an anti-tank gun on its own carriage, as well as equipping a number of British tanks.
 It was the most effective anti-tank gun of the war fielded by the Western Allies (that is, excluding the Soviet Union).
 Used with the APDS shot, it was capable of defeating all but the thickest armour on German tanks.
 It was used to 'up-gun' some foreign-built vehicles in British service, notably to produce the Sherman Firefly variant of the US M4 Sherman tank, giving British tank units the ability to hold their own against their German counterparts.
 In the anti-tank role, it was replaced after the war by the 120 mm BAT recoilless rifle.
 As a tank gun, it was succeeded by the 84 mm 20 pounder.
The 76 mm gun M1 was an American World War II–era tank gun developed by the U.S Ordnance Department in 1942 to supplement the 75 mm gun on the basic Medium tank M4.
 It was also used to arm the 76 mm Gun Motor Carriage M18 tank destroyer.
Armour-piercing discarding sabot (APDS) is a type of kinetic energy projectile fired from a rifled-barrel gun to attack armoured targets.
 APDS rounds are sabot rounds, firing a spin-stabilized armor penetrating sub-projectile, and were commonly used in large calibre tank guns, up until the early 1980s, but have now been superseded by armour-piercing, fin-stabilised, discarding sabot (APFSDS) projectiles used in smooth-bore guns, firing a fin-stabilized armor penetrating sub-projectile.
 However, APDS rounds are still commonly used in small or medium calibre weapon systems.
 For a given calibre, this type of ammunition can effectively double the armour penetration of a gun, compared to those firing armour-piercing (AP), armour-piercing, capped (APC), or armour-piercing, capped, ballistic capped (APCBC) projectiles.
 The saboted light armour penetrator (SLAP) concept applies this technology to small arms calibres.
The 7.5 cm KwK 42 L/70 (from "7.5 cm Kampfwagenkanone 42 L/70") was a 7.5 cm calibre German tank gun developed and built by Rheinmetall-Borsig AG in Unterlüß during the Second World War.
 The gun was used to equip the SdKfz.171 Panzerkampfwagen V Panther medium tank and the SdKfz.162/1 Jagdpanzer IV/70(A)/(V) tank destroyer.
 When mounted on a tank destroyer it was designated as the 7.5 cm Pak 42 ("7.5 cm Panzerabwehrkanone 42") anti-tank gun.
The 76 mm tank gun M1940 F-34 ("76-мм танковая пушка обр.
 1940 г.
 Ф-34") was a 76.2 mm Soviet tank gun used on the T-34/76 tank.
 A modified version of the gun, the 76 mm tank gun M1941 ZiS-5 ("76-мм танковая пушка обр.
 1941 г.
 ЗиС-5"), was used on KV-1 tanks during World War II.
 Nowadays, the two versions are often referred to just by their factory designations, as "F-34" and "ZiS-5", respectively.
The 8.8 cm KwK 43 L/71 (Kampfwagenkanone —"fighting vehicle cannon") was an 88 mm 71 calibre tank gun designed by Krupp and used by the German Wehrmacht during the Second World War.
 It was mounted as the primary armament on the Panzerkampfwagen VI Ausf.
 B "Tiger II" and the 8.8 cm PaK 43, an anti-tank gun, was very similar in design and use albeit not mounted on tanks but rather on tank destroyers or deployed on the field.
The Krupp family (see pronunciation), a prominent 400-year-old German dynasty from Essen, have become famous for their production of steel, artillery, ammunition, and other armaments.
 The family business, known as Friedrich Krupp AG, was the largest company in Europe at the beginning of the 20th century.
 It was important to weapons development and production in both world wars.
 One of the most powerful dynasties in European history, for 400 years Krupp flourished as the premier weapons manufacturer for Germany.
 From the Thirty Years' War until the end of the Second World War, they produced everything from battleships, U-boats, tanks, howitzers, guns, utilities, and hundreds of other commodities.
The D-10 is a Soviet 100 mm tank gun developed in late World War II.
 It originally equipped the SU-100 tank destroyers and was later selected for the T-55 tank, equipping these as late as 1979.
 On the T-55 the D-10 continues to be in active service in many countries.
The Uralmash-1 (Уралмаш-1) was a Soviet prototype self-propelled gun developed during World War II.
 It was a turretless, tracked armoured fighting vehicle designed by the Yekaterinburg-based Uralmash design bureau (UZTM) between autumn 1944 and spring 1945.
 It used the chassis of the T-44 medium tank and was intended to replace the SU-100 which itself had only entered service with the Red Army in late 1944.
 Two prototypes of the Uralmash-1 with different armament were built in early 1945, one with the 100 mm D-10 tank gun, the other with the 122 mm D-25S tank gun.
 While mass production was initially recommended, the end of the war with Germany in May 1945 eventually caused the project to be cancelled due to lack of necessity.
 If the Uralmash-1 had entered service, the 100 mm variant would have been designated SU-101 (СУ-101) while the 122 mm variant would have been designated SU-102 (СУ-102), in accordance with Soviet military nomenclature, where the "SU"-label stood for Samokhodnaya Ustanovka, or self-propelled gun.

Question: For which war was the 71 calibre tank gun developed by a prominent 400 year old German dynasty?
Answer: Second World War