The Sturmgeschütz III (StuG III) assault gun was Germany's most produced armoured fighting vehicle during World War II. It was built on the chassis of the proven Panzer III tank. Initially intended as a mobile, armoured light gun for infantry support, the StuG was continually modified and was widely employed as a tank destroyer.
The vehicles of the Sturmgeschütz series were cheaper to build than the contemporary German tanks; at 82,500 RM, a StuG III Ausf G was cheaper than a Panzer III Ausf. M which cost 103,163 RM to build. By the end of the war, 10,619 StuG III and StuH 42 had been built.
The Sturmgeschütz III originated from German experiences in World War I when it was found that during the offensives on the western front the infantry lacked the means to effectively engage fortifications. The artillery of the time was heavy and not mobile enough to keep up with the infantry to destroy bunkers, pillboxes, and other obstacles, with direct-fire. Although the problem was well-known in the German army it was General Erich von Manstein who is considered the father of the Sturmartillerie. This is because the initial proposal was from (then) Colonel Erich von Manstein and submitted to General Ludwig Beck in 1935, suggesting that Sturmartillerie ("assault artillery") units should be used in a direct-fire support role for infantry divisions. On June 15, 1936 Daimler-Benz AG received an order to develop an armoured infantry support vehicle capable of mounting a 75 mm (2.95 in) artillery piece. The gun was to have a limited traverse of a minimum of 25 degrees and be mounted in an enclosed superstructure that provided overhead protection for the crew. The height of the vehicle was not to exceed that of the average man.
Daimler-Benz AG used the chassis and running gear of its recently designed Panzer III medium tank as a basis for the new vehicle. Prototype manufacture was passed over to Alkett, which produced five examples in 1937 of the experimental 0-series StuG based upon the Panzer III Ausf. B. These prototypes featured a mild steel superstructure and Krupp’s short-barreled 75 mm Sturmkanone 37 L/24. This model was known as the Sturmgeschütz Ausführung A.
While the Stug was considered self-propelled artillery it was not initially clear which arm of the Wehrmacht would handle the new weapon. The Panzer arm, who was the natural user of tracked fighting vehicles, had no resources to spare for the formation of Stug units, and neither did the Infantry branch. It was therefore agreed, after a discusion, it would best be employed by becoming a part of the artillery arm.
The Stugs were organised in Battalions (later renamed "Brigades" for disinformation purposes) and followed their own specific doctrine. Infantry support using direct-fire was its intended role, and later there was also strong emphasis on destroying enemy tanks whenever encountered.
As the StuG III was intended to fill an infantry close support combat role, early models were fitted with a low-velocity 75 mm StuK 37 L/24 gun to destroy fortifications. After the Germans encountered the Soviet KV and T-34, the StuG III were armed with the high-velocity 75 mm StuK 40 L/43 (Spring 1942) or 75 mm StuK 40 L/48 (Autumn 1942) anti-tank gun. These versions were known as Sturmgeschütz 40 Ausführung F, F/8 and G.
When the StuG IV entered production in late 1943, early 1944, the "III" was added to the name to separate them from the Panzer IV based assault guns. All previous and following models were thereafter known as 'Sturmgeschütz III'.
In 1944 the Finnish Army received 59 StuG III Ausf. G from Germany (30 Stu 40 Ausf.G and 29 StuG III Ausf. G) and used them against the Soviet Union. These destroyed at least 87 enemy tanks for a loss of only 8 StuGs (some of these were destroyed by their crews when they abandoned the vehicle to prevent capture). After the war they were the main combat vehicles of the Finnish Army until the early 1960s. These StuGs gained the nickname "Sturmi" which can be found in some plastic kit models.
Sturmgeschütz IIIs were also exported to other nations like Bulgaria, Hungary, Italy, Romania, and Spain.
In 1942, a variant of the StuG III Ausf. F was designed with a 10.5 cm (105 mm) howitzer instead of the 7.5 cm StuK 40 L/43. These new vehicles, designated Sturmhaubitze 42 (10.5 cm StuH 42, Sd.Kfz 142/2), were designed to provide infantry support with the increased number of StuG III F/8 and Gs being used for anti-tank duties. The StuH 42 mounted a variant of the 10.5 cm leFH 18 howitzer, modified to be electrically fired and fitted with a muzzle brake. Later models were built from StuG III G chassis as well as StuG III F and F/8 chassis. The muzzle brake was often deleted as well because of the scarcity of resources. 1,211 StuH 42 were produced from October 1942 to 1945.
In 1943, 10 StuG IIIs were converted to StuG III (Flamm) configuration by replacing the main gun with a Schwade flamethrower. These chassis were all refurbished at the depot level and were a variety of Pre-Ausf. F models. There are no reports to indicate any of these were used in combat and all were returned to a Stug III G standard at depot level by 1944.
In late 1941 the StuG III chassis was selected for an attempt to mobilize the 15 cm sIG 33 heavy infantry gun. From December 1941 to October 1942 Ausf. E and F chassis (12 each) received a modified superstructure to accommodate the larger gun. These vehicles were known as Sturminfanteriegeschütz 33. At least twelve vehicles saw combat in the Battle of Stalingrad where they were destroyed or captured.
In January 1944, the StuG IV, based on the PzKpfw IV chassis and with a slightly modified StuG III superstructure entered production.
The Soviet SU-76i self-propelled gun was based on captured StuG III and Panzer III vehicles . In total, Factory #37 in Sverdlovsk manufactured 181 SU-76i plus 20 commander SU-76i for Red Army service by adding an enclosed superstructure and the 76.2 mm S-1 tank gun.