The Sturmgeschutz III (StuG. III) was a German anti-tank, armored vehicle of the Second World War. Built on the chassis of the proven Panzer III tank, the Sturmgeschutz was originally intended as a support weapon for attacks by non-armored infantry. Nevertheless, with the eruption in the battlefield of the Soviet T34, KV I and KV II tanks, the Sturmgeschutz III proved to inadequate by late 1941, especially during the Battle of Moscow. These Russian tanks had thicker armor, faster speed, and long range trajectory from long barelled guns. The short 75mm gun (Stuk L/24) of the StuG III was effective only against soft-armored vehicles with little maneuverability.
A longer gun and better characteristics was what was needed. Accordingly, a new version of the Sturmgeschutz III was developed. By May 1942, the new anti-tank vehicle was ready; it was the Sturmgeschutz III Ausf F. Powered by a 300 hp Maybach HL120TRM V-12 gasoline engine, the StuG III Ausf. F was fitted out with a longer and more powerful 75mm gun; the StuK L/43. This new gun fired armor piercing Panzergranat-Patrone 39, which could pierce through 91mm of armor inclined 30º from vertical at 500m (550 yards), 82mm at 1000m, 72mm at 1500m, and 63mm at 2000m (2 km, or 1.5 miles). Thus, the new StuK L/43 gun of the Ausf. F allowed the Sturmgeschutz to engage most Soviet armors at normal combat ranges.
Between September and December 1942, the Wehrmacht built a new model the Sturmgeschutz; the StuG III Ausf. F/8, which was equipped with another yet more powerful 75mm gun as 30mm-thick additional armors were bolted on to protect the vehicle from enemy armor-piercing round. The 75mm StuK 40 L/48 was fitted with single baffle ball type muzzle brake because it lacked double baffle muzzle brakes.
By the end of December 1942, a new model of the Sturmgeschutz III was already operational. This was the StuG III Ausf. G, which was equipped with the same canon used by the Ausf. F/8, but it was mounted in a strong steel base called "Saukopf Mantlet". The upper superstructure of the StuG III Ausf. G was widened as welded boxes on either sides were abandoned. This new superstructure design increased its height to 21,60cm. Backside wall of the fighting compartment was straightened, and ventilation fan on top of the superstructure was relocated to the back of fighting compartment. From March 1943, driver’s periscope was abandoned. From May 1943, side hull skirts were fitted to G models for added armor protection particularly against anti-tank rifles. From May 1943, 80mm thick plates were used for frontal armor instead of two plates of 50mm+30mm.