The British STEN submachine gun is one of those rare firearms in history that was born of desperation and turned into a war-winning endeavor. The STEN was a widely-produced personal weapon system (noted as a "machine carbine" but generally categorized as a "submachine gun") of British origin serving during World War 2. The weapon was designed around the principles of cheap production and simplicity in both its operation and assembly. It proved a no-frills submachine gun designed exclusively for medium-to-close-combat ranges and spawned an entire family of firearms owning their design to the original initiative. The general design was nothing more than a tubular metal receiver housing the internal working components capped by a barrel at one end a rudimentary shoulder support at the other while being actuated through a primitive-looking trigger group - many forms lacking a conventional pistol grip. Despite its utilitarian appearance and basic function (as well as awkward layout and feed-jamming issues), the STEN became a popular submachine gun for British and Commonwealth forces throughout the war. The type even saw production by the Germans in the thousands during 1944 (a German offshoot also appeared in 1945).
The British military lent its support to the faltering fronts across Europe in the summer of 1940. However, all of the initiative proved disastrous when Allied forces were cornered at the sea-side port of Dunkirk which forced a massive rescue operation from sources in England. While the German Army failed to pulverize the survivors caught on shore, it managed to capture tons of Allied equipment - tanks, artillery, small arms and the like. What became war-booty to the victorious Axis proved another logistical peril for the British as the loss of such valuable equipment, coupled with the fall of France, provided little defense for the British mainland, knowing full well that the Germans would not stop at the coast - intent to conquer the English by land and air.
Without delay, the British government authorized local production of the German MP28, a capable submachine gun with origins in the World War 1-era MP18. At this point in the war, the British military lacked any frontline submachine gun weapon system of which the Germans put to good use in their Blitzkrieg operations. Instead, the British infantryman relied largely on their tried-and-true yet cumbersome and outdated bolt-action service rifles. The local-production MP28 became known to the British as the "Lanchester" after production director George H. Lanchester. There were slight variations added to the local attempt, principally in the barrel rifling and support for the Lee-Enfield field bayonet.
Elsewhere, work had proceeded on an indigenous new British submachine gun design based on findings of the respected German MP38 submachine gun series. The MP38 entered service with the Germans in 1939 and fired the effective 9x19mm Parabellum pistol round from a straight blowback, open bolt arrangement. Hundreds of thousands of the type were ultimately produced and served as the standard German submachine gun of World War 2. The submachine gun proved highly effective and gave the Germans an early advantage in their portable automatic weapons. However, the original MP38 was a complex beast which made it expensive to produce in the numbers required (which led to the simplified MP40).
With that said, the British effort was led by Major Reginald V. Shepherd and Harold J. Turpin and took to a design in the MP38 mold that was substantially cheaper to produce and would be just as rugged and reliable in-the-field. The design made use of a pressed steel metal frame with spot welding throughout. This produced a crude, yet adequate, personal weapons system that could stock the British inventory in the hundreds of thousands. Trials of a prototype model ensued in January of 1941 and the weapon was formally accepted into service and subsequent serial production thereafter. The weapon would be known as the "STEN" formed of the last name initials of Shepherd and Turpin ("S" and "T") and the first two letters of the place of origin - Enfield Lock ("EN"). The arrival of the STEN forced the Lanchester design into the background and it only went on to serve with the British Royal Navy. Precedence was given to the economical STEN and production lines ramped up for the expected numbers through Enfield Lock as well as other Royal Ordnance facilities throughout Britain (over a dozen contractors and sub-contractors eventually took part).
All STEN guns were chambered for the 9x19mm Parabellum pistol cartridge.
The initial production form became the STEN Mk I. This version was identified by their dedicated barrel jacket (encasing the barrel assembly), skeletal butt, tubular fold-down wooden forward grip, removable barrel and wooden forend. A spoon-shaped flash hider was added to the barrel to help conceal the firing position of the operator, particularly useful during night operations. The flash hider doubled as a muzzle compensator which was to aid in muzzle climb during full-automatic fire and, therefore, assist in accuracy at range. The 32-round detachable straight magazine was inserted into the feed located on the left side of the receiver with spent shell casings ejecting from the right. Roughly 100,000 of the Mk I model were produced before the arrival of the simplified and lighter STEN Mk I* - which did away with the wooden furniture, wooden foregrip and clumsy muzzle attachment.
Engineers continued their work on the STEN family of guns and this ultimately produced the definitive STEN in the STEN Mk II. This version included a relocated safety while the barrel jacket was removed in favor of a more simplified perforated heat shield. The magazine feed was revised to include a 90-degree "swivel-down" position in which the magazine could be stowed aside when not in use, making for less clumsy cargo when on the march. The STEN Mk II saw over two million examples produced over a three-year span and the cost-savings measures certainly allowed for this level of serial production.
A silenced STEN Mk II variant was then realized and designated as the STEN Mk IIS primarily for use with special forces operatives. The use of a silencer on the STEN was one of the rare wartime accounts concerning automatic weapons. The STEN Mk IIS essentially replaced the normal barrel assembly of the Mk II with a cylindrical silencer housing a shorter barrel intended to release each bullet at subsonic speeds and, hence, at a more silent decibel level. While this arrangement did, in fact, produce a quieter weapon, its overall range was expectedly reduced. The internal working components - the spring and bolt - were lightened to further reduce operational noise. The STEN Mk IIS was essentially limited to single-shot fire for automatic fire led to a premature weakening or breakage of the silencer assembly. Beyond the added cylinder, and perhaps padding added around the assembly to function as a forward grip, the STEN Mk IIS looked largely like its basic STEN Mk II counterpart.
The STEN Mk III continued to lighten and simplify overall production and was based more on the STEN Mk I than the improved STEN Mk II. First appearing in 1943, the variant saw the removable barrel feature dropped and did not include the positional magazine feed functionality, becoming more of a basic, single-piece, welded and reinforced tubular body made of sheet-steel. This gave the Mk III a more sleeker and uniformed receiver/heat-shield appearance. A finger guard was added near the ejection port to protect the firer's hand from spent shell casings being flung out. Production of STEN MK IIIs was handled in Canada as well as Britain and even captured Mk IIIs by the Germans were reconstituted as the MP.750(e).
The STEN Mk IV appeared in 1943 as a proposed airborne infantry variant that was never selected for serial production though the mark proceeded as far as prototypes. The design took the STEN MK II and produced a dimensionally smaller end-product for increased portability - a quality appreciated by paratroopers. The barrel was appropriately shortened and a folding butt was added. The STEN Mk IV would have been produced in an Mk IVA and Mk IVB version, each differentiated by their grips and trigger units. However, the decision was made against pursuing the Mk IV design.
The STEN Mk V appeared in 1944 and bought back use of the pistol grip and a full shoulder stock as well as mounting for a service rifle bayonet for close-quarters work. This was all in an attempt to make the STEN MK V a more favorable weapon to British troopers who held a certain disdain for the basic appearance of the original STEN guns. Machining was properly fine-tuned and finishing details returned along the production lines. Changes incorporated a wooden pistol grip, forward grip and wooden butt which made it more akin to other acceptable submachine gun types around the world. The front sight was lifted from the No. 4 service rifles and support for the standard British field bayonet was included. While intended as an improvement over the STEN Mk II series, the Mk V came in weighing heavier thanks to its additional wood furniture and the magazine feed issues persisted while the forward hand grip was prone to breaking off in the heat of battle (the foregrip eventually dropped from production).
The STEN Mk VI became the silenced version of the Mk V. The silencer assembly was the same as featured in the STEN Mk IIS while the internals and frame were retained from the Mk V. Few of this form saw service.
Despite entering operational service in 1941, the STEN was not used in direct-enemy combat until 1942 when British and Allied elements (largely Canadian) participated in the disastrous Dieppe amphibious assault on August 12th. Losses included 3,367 Canadians along with 275 British special forces elements to the German's 311 KIA. While the assault was a complete failure for the Allies and a resounding victory for the Germans, the STEN gun was a proven commodity under battlefield conditions. The Dieppe Raid also served as a launching point to the heralded D-Day invasion landings of Normandy in North France of June 1944.
In practice, initial British impressions were mixed for the utilitarian finish and outward appearance of the weapon left much to be desired. It was only in consistent operational service that the STEN family shined, capable of rough in-the-field service and adequate reliability while providing voluminous fire from a relatively easy-to-handle frame. The STEN did suffer from lingering misfeeds which led to jamming, an issue with the family that was never wholly resolved in all of the war. A full 32-count magazine was capable of producing this effect which led to many service members utilizing only 30 rounds (less pressure on the magazine spring). Additionally, the heat of battle saw operators making use of the side-protruding magazine as a forward grip to which, with enough tight pressure, could unseat the magazine from its feed, causing a jam at the worse possible moment. As such, operators were generally taught the proper method of holding their STENS which involved the support hand under the barrel heat shield with the magazine resting on the bent supporting arm, the butt against the shoulder and the primary hand at the trigger area as normal.
By 1945, over 4 million STEN guns had been manufactured in its various production marks. The weapon saw use beyond that of organized military establishments for they proved equally popular with partisan movements, rebel groups and individuals requiring high-volume fire from a compact package. They certainly made for excellent urban fighting guns where space was limited and the weapon could also be hauled with ease through forest terrain without fear of snagging. The simplicity of the STEN's overall design meant that it could be taken apart into its basic components, transported under the nose of enemy authorities and reassembled as needed, made ready to fire within minutes.
The German concern of Mauser locally-produced STEN Mk II guns as exact copies (complete with English markings) for possible use by special operatives. Some 28,000 were produced under the name of "Gerat Potsdam". A cheaper, late-war alternative appeared in 1945 as the "MP 3008" of which 10,000 examples were produced by various entities for arming the general populace and defense forces in the final battle of Germany/Berlin against the impending Allied invasion.
STEN submachine guns lasted into the 1960s and were, in British service, replaced by the Sterling series. STENs elsewhere persisted much longer and saw war throughout the various conflicts of the Cold War - including both the Korean War and the Vietnam War as well as the Indo-Pak wars. The STEN also saw various production forms emerge from developing/reconstructing countries in the post-war years including Argentina, Australia, Belgium, France, Norway, Denmark and Poland among others - each noted with their own respective designations. Also consider that the weapon was produced by various underground movements during the years of occupation.