The 21 cm Kanone 12 in Eisenbahnlafette (21 cm K 12 (E)) was a large German

railroad gun Rail transport (also known as train transport) is a means of transport that transfers passengers and goods on wheeled vehicles running on rails, which are incorporated in tracks. In contrast to road transport, where the vehicles run on a prep ...

used in the

Second World War World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposi ...

and deployed to fire on

England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe ...

from the

English Channel The English Channel, "The Sleeve"; nrf, la Maunche, "The Sleeve" ( Cotentinais) or ( Jèrriais), ( Guernésiais), "The Channel"; br, Mor Breizh, "Sea of Brittany"; cy, Môr Udd, "Lord's Sea"; kw, Mor Bretannek, "British Sea"; nl, Het Ka ...

coast in

occupied France The Military Administration in France (german: Militärverwaltung in Frankreich; french: Occupation de la France par l'Allemagne) was an interim occupation authority established by Nazi Germany during World War II to administer the occupied z ...

Design and history

Krupp The Krupp family (see pronunciation), a prominent 400-year-old German dynasty from Essen, is notable for its production of steel, artillery, ammunition and other armaments. The family business, known as Friedrich Krupp AG (Friedrich Krupp ...

continued theoretical research on a replacement for the

Paris Gun The Paris Gun (german: Paris-Geschütz / Pariser Kanone) was the name given to a type of German long-range siege gun, several of which were used to bombard Paris during World War I. They were in service from March to August 1918. When the guns w ...

during the

Weimar Republic The Weimar Republic (german: link=no, Weimarer Republik ), officially named the German Reich, was the government of Germany from 1918 to 1933, during which it was a Constitutional republic, constitutional federal republic for the first time in ...

-era, but it was the Nazi government that finally authorized funding for experiments to solve some of its worst problems. The extremely high velocities used by the Paris Gun to attain the

stratospheric The stratosphere () is the second layer of the atmosphere of the Earth, located above the troposphere and below the mesosphere. The stratosphere is an atmospheric layer composed of stratified temperature layers, with the warm layers of air h ...

heights necessary for extreme range caused enormous wear of the barrel, so much so that the shells had to be made in gradually increasing diameter to suit the rate of wear. Even then barrel life was merely 65 rounds. It is believed that the one Paris Gun destroyed by a premature detonation in the bore was caused by loading one of the serially-numbered shells out of order. Thus Krupp decided to use only eight grooves in the barrel and to machine matching ribs or splines on the shells to eliminate the need for a massive copper driving band to start the shell spinning without shearing off, which had been one of the prime causes of the excessive barrel wear in the earlier weapon. Gas sealing would be handled by a copper band, mounted in the place normally occupied by the driving band, with an

asbestos Asbestos () is a naturally occurring fibrous silicate mineral. There are six types, all of which are composed of long and thin fibrous crystals, each fibre being composed of many microscopic "fibrils" that can be released into the atmosphere b ...

and

graphite Graphite () is a crystalline form of the element carbon. It consists of stacked layers of graphene. Graphite occurs naturally and is the most stable form of carbon under standard conditions. Synthetic and natural graphite are consumed on la ...

packing to form the initial seal. Several test barrels, known as the 10.5 cm K 12 M, and shells were made in 1935 and were compared to a conventionally rifled barrel (the 10.5 cm K 12 MKu). The tests proved that Krupp's concept was correct. The K 12 (E) was mounted on a simple box-girder carriage, which was carried on two subframes which were in turn mounted on double bogies. The barrel was mounted in a ring cradle with a hydropneumatic recoil system. Two more hydropneumatic systems were connected to the subframes, which allowed the entire carriage to recoil some . For transport the gun itself was disconnected from its recoil system and drawn back some to reduce the mounting's overall length and allow it to fit in the normal railroad loading gauge. The barrel's extreme length required external bracing to prevent it from bending under its own weight. Its

trunnions A trunnion (from Old French "''trognon''", trunk) is a cylindrical protrusion used as a mounting or pivoting point. First associated with cannons, they are an important military development. Alternatively, a trunnion is a shaft that positions ...

were placed as far forward as possible to balance the barrel and minimize the force necessary to elevate it. This placed the breech perilously close to the ground and a hydraulic jacking system was built in each subframe to elevate the mount . However it was impossible to load the weapon in this position and it had to be lowered between every shot. The K 12 (E) could be fired from any curved section of track, a Vögele turntable, or from its special firing track. This prefabricated T-shaped track was carried on the gun train and deployed by a special crane wagon. Once the front bogies were at the crossover at the top of the T they were then jacked up and turned with the subframe 90° and then lowered onto the crosstroke of the T. The gun was then traversed by an electric motor to the bogies and it was clamped to the track once laid onto the target. It fired HE shells weighing . The first weapon was completed in 1938 and delivered to the

Army An army (from Old French ''armee'', itself derived from the Latin verb ''armāre'', meaning "to arm", and related to the Latin noun ''arma'', meaning "arms" or "weapons"), ground force or land force is a fighting force that fights primarily on ...

in March 1939. It was successful, although the necessity to jack it up and down between shots was not well received by the Heer. Krupp discovered, on trying to rectify this problem, that hydro-pneumatic balancing-presses could work at much greater weights and pressures than previously believed. They redesigned the mounting with the trunnions as far forward as possible and increased the recoil stroke to . The new design was delivered in mid-1940 and called the K 12 N (E). The first gun was retrospectively called the K 12 V (E). They spent the war assigned to Artillerie-Batterie 701 (E) along the Channel coast. The British recovered shell fragments near Rainham, Kent, from the nearest point on the French coast.

Design and history

References

Further reading