The first 24 StuG III Ausf A’s produced equipped Sturmartillerie Batteries 640, 659, 660 and 665 and first saw service during the French Campaign. Each battery had six assault guns in three platoons (with two assault guns each). Sturmartillerie Battery 640 became organic to Infantry Regiment Grossdeutschland and was renamed to 16th Sturmartillerie. The last six assault guns were issued to SS Sturmartillerie battery of Leibstandarte SS Adolf Hitler division. Two more batteries were formed - 666th and 667th but didn't see combat in France.
In August of 1940, Sturmartillerie units were reorganized into Abteilungen (battalions) with 18 assault guns in three batteries (with six assault guns each).
In early 1941, the battalions were renamed to Sturmgeschütz Abteilungen and batteries to Sturmgeschütz Batteries. Each Abteilung still consisted of three batteries of six guns each.
In spring of 1941, all Sturmgeschütz Batteries had the number of assault guns increased to seven.
In 1942, with the introduction of long-barreled StuG III (75mm L/43 and L/48), Sturmgeschütz Abteilungen were reformed and number of assault guns was increased to 28 per battalion. Each battalion still had three batteries but the number of assault guns in platoons was increased to three.
In November of 1942, Sturmgeschütz Abteilungen were reformed again and the number of assault guns was increased to 31 per battalion with three additional assault guns for battery commanders. This type of organization often referred to as Sturmgeschütz Brigade remained in use until the end of the war.
In June of 1944, new organization scheme was introduced - Sturmartillerie Brigade with 45 assault guns, including 33 StuG III/IV (75mm L/48) assault guns and 12 Sturmhaubitze 42 (105mm L/28) assault howitzers. The brigade had three batteries with two StuG III’s for each battery command, while each battery had two platoons of four StuG III’s and one of four StuH 42s. This organization scheme was used alongside the Sturmgeschütz Brigade scheme to the end of the war. In practice, these ideals were hardly ever achieved and then only highly favored formations received the full complement.
Towards the end of the war, StuGs (40) were often issued to other units as replacement for tank destroyers and even tanks. Since 1944, StuG III (40) were also used as replacements for PzKpfw III, PzKpfw IV and even PzKpfw V Panther in Panzer Abteilungen.
During the course of war, StuG III assault guns were issued to Sturmartillerie Batteries, Sturmgeschütz Abteilungen, Sturmgeschütz Brigades, Sturmartillerie Brigades, Ersatz (Reserve) Abteilungen and Funklenk (Remote Control) Companies. StuG III assault guns served on all fronts of WWII to the end of the war. Only, elite Wehrmacht (e.g. Grossdeutschland) and Waffen SS (e.g. LSSAH, Das Reich, Totenkopf) divisions had Sturmgeschützbrigaden as permanent part of their divisions.