STG is shorthand for "
Sturm Gewehr" which literally translates to "Assualt Rifle". Since this was the first appearance of the word "Assualt Rifle" it was come to be known as the first assualt rifle in the world (simultaneously coining the phrase "assualt rifle").
As early as 1934 the need for a compact selective fire weapon was shown to be necessary but encountered opposition from staff officers and also from Adolf Hitler himself who preferred the
infantryman to use the traditional weapon of
the rifle as he had done during W.W.I. This bias
hampered the development of this weapon up to the end of the war.
A prototype was not ready until 1940 due to problems with a suitable cartridge design and after several experiments with different size cartridges, it was decided to use the standard size rifle round with a shortened cartridge (
kurz) and make the necessary adjustments to the rifle design. The cartridge was known as the 7.92mm Infanterie
Kurz Patrone 7.92 x 33mm (Standard was 7.92 x 57mm).
The initial contract was given to
C.G.
Haenel who started work on a weapon known as Maschinenkarabiner (
Mkb) with Hugo Schmeisser (of
MP40 fame) being the lead engineer on this project. By 1941 a prototype was ready, basically a gas operated rifle produced from pressings which were subcontracted out to the steel fabrication firm
Mertz Werke. An order was placed for 50 pre-production weapons was filled.
Preproduction orders were placed with both Haenel and
Walther (who had also been working on semi-automatic rifle design G41 and G43) which included guidelines that had to be adhered to. These guidelines included providing a suitable fitting for the standard rifle
bayonet, standard muzzle threads and the Haenel magazine these were to be adhered to by both companies.
Production of the weapon was however very poor and by 1943 only a few thousand had been produced. There were some distinct differences between the two designs firing mechanisms with the Walther model using an annular gas piston with a sleeve to connect
the bolt (which also acted as a means of cocking the rifle). The Haenel design incorporated the much better conventional type of
long stroke piston which drove back the bolt carrier, causing it to tip the rear bolt upwards out of it's locking recess.