Prototypes of the StG 44 were in advanced testing stages as early as 1942, but were never put into production until mid-1943 because of opposition from Hitler himself. To circumvent Hitler's opposition, manufacturers renamed the StG 44 as the MP 43 and MP 44, claiming them to be machine pistols as a cover from Hitler. The rifle was first used on a mass scale when a German battalion was surrounded by Soviets near Leningrad, so the Luftwaffe air-dropped many MP 43s and the battalion fought their way out.
Confused, Hitler flew out to the front lines to inspect troops; he was surprised with this new gun and liked it so Hitler changed the name to StG 44 and used it in his "wonder weapon program" to raise German morale. There is no clear indication why exactly Hitler was averse to this design, as the weapon had excellent design, even nowadays.
The StG 44 fired 7.92x33mm (7.92 Kurz) ammunition, stored in 30 round magazines.
The StG 44 would see combat in all fronts, especially the Eastern Front, against the Red Army. Upwards of 400000 weapons were produced; it didn't change the course of the war, but it made a great impact on weapons development. Many of its features would be incorporated in other weapons, like the M16; the FN FAL; and the AK-47, the latter being developed around the concept of the assault rifle idea, from which the StG 44 came from.
In postwar years, it was used by the armies of East Germany; Czechoslovakia; and Yugoslavia, until replaced by AK-type weapons, with Czechoslovakia adopting the vz. 58 assault rifle; it would see combat in Somalia; Ethiopia; and even today, in Syria, at the hands of anti-government forces. In Europe, surviving weapons were converted to fire in semi-auto only and are being sold to civilians; even newly made versions, built from scratch, have been manufactured in Germany.