selfpropelledguns

The main idea behind the design of the Wespe was to provide all mobile formations with proper and indirect artillery support. Like artillery, Wespe operated in batteries and received orders and directions from forward observers by radio or field telephone, reducing the risk of being exposed to direct enemy fire.
The Wespe were built on redundant PzKfw II chassis, with the engine moved forward to a more central location and the suspension reinforced in order to absorb the stress from firing recoil. Subsequent versions were based on a modified chassis with a slightly lengthened hull to improve vehicle stability.
The gun was mounted in the centre of an open-topped armoured superstructure constructed over the engine and behind a gun shield. The superstructure itself was made up of 10mm plates, which provided limited protection for the crew and storage for 32 rounds of ammunition. Space inside the fighting compartment was cramped and there was not much space to operate the gun. The gun itself could be traversed 17º to the left and right and elevated from -5º to + 42º. The 105mm leFH 18 was able to fire high explosive, shaped charge and armour piercing ammunition and had an effective range of 8400m. A 7.92mm MG34 machine gun was issued to crews and carried inside the fighting compartment for local defence.
The five man crew composed of a driver, commander and three gunners. Gunners were also trained to act as a driver and radiomen if needed. The driver sat in his own compartment in the front of the vehicle to the left side of the gun. His compartment was fully enclosed and had separate access, while the commander and three gunners were located in the fighting compartment.
In order to supply Wespe batteries with ammunition in the field, an unarmed ammunition carrier, was produced. The vehicle was a regular Wespe without the main armament, however this could be mounted if needed and the conversion could be completed in the field. The vehicle carried 90 rounds of ammunition and was operated by a crew of three.
Production of the Wespe ended in August of 1944 and the vehicle remained in service until the end of the war.
Wespe were issued to Panzer Division artillery batteries from the spring of 1943. Each battery consisted of six Wespe and two Wespe ammo carriers.

Based on the experiences gained in the early stages of fighting on the Eastern Front, development of an artillery support vehicle based on the PzKfw III chassis began in early 1942.
Production of the vehicle began in July 1942 and it entered service in March 1943. The vehicle was based on a special chassis which combined components of both the PzKpfw III driving and steering mechanism and the PzKpfw IV suspension, engine and cooling system.
In order to provide a fighting compartment, the chassis was slightly lengthened and the engine was moved forward to a more central location. The crew travelled in the open-top compartment with all its weather-related disadvantages. Some vehicles were mounted with the frame skeleton over the fighting compartment covered with mesh wire. Hummels lacked a machine gun in the hull, so a single 7.92 MG was carried inside the fighting compartment for local defence. In early 1944, the front superstructure and driver's compartment were redesigned, allowing more space for both the driver and radio operator. In addition the exhaust system was modified.
The Hummel suffered from having a limited ammunition storage capability, so in 1943 Hummel ammunition carriers were built. The main armament was removed and the fighting compartment was fitted with ammunition racks. The vehicle was still able to mount the howitzer if needed and the conversion could be completed in the field.
Hummels were issued to the Heavy Self-Propelled Artillery Battery of the Panzer Division artillery Batallion. Each Battery six Hummels and one Munitionstrager Hummel. Although production ended in 1944, Hummels remained in service until the end of the war.

In 1935, it was proposed that Sturmartillerie units were to be formed and used for direct support of infantry divisions. They were to be equipped with assault guns mounted on a tracked chassis and used to accompany the infantry into the attack. The assault gun's main aim was to knock out strong points, machine gun nests, anti-tank guns and other obstacles. Assault guns were simpler, cheaper and less time consuming to produce than turreted tanks and that is why German factories built them in large numbers.
In June 1936, development began of an armoured infantry support vehicle mounting a 75mm gun. The gun was to have a limited traverse of 25°, in order to provide direct support. The gun was to be mounted in a superstructure that provided full protection for the crew.
The first vehicles, based on the PzKfw III Ausf F chassis, entered production in 1940. They were armed with the 75mm StuK 37 L/24 gun, mounted offset to the right in a sloped superstructure. The superstructure was made of armour plates and was mounted on the welded hull. Frontal hull and superstructure armour protection was 50mm.
The Ausf A was followed by improved Ausf B, C, D and E variants, all armed with short 75mm StuK 37 L/24 gun. All versions featured a number of modifications and improvements. Many early models were recalled to the factory to be rearmed with newer guns and up-armoured by addition of armour plates. The Stug III Ausf E was the first of the series to be provided with 7.92mm MG34, which was carried inside the superstructure for local defence.
In March of 1942, Ausf F entered production. It was not only an assault gun but also a badly needed tank destroyer. It was mounted with a new 75mm StuK 40 L/43 gun. The long 75mm gun allowed assault guns to combat tanks and also afforded greater accuracy at longer ranges. The Ausf F was then replaced by the Ausf F8, armed exclusively with the 75mm L/48 gun.
In May 1943, 10 battle damaged Stug III Ausf F/8's, were converted into flame-thrower tanks armed with a 14mm Flammenwerfer. They were designated as Sturmgeschutz III (Fl).
The Ausf G entered production in December 1942. It used the Ausf F hull, suspension and engine, while the superstructure was modified. The superstructure was widened, its 30mm sides were sloped at 79°, the roof was raised in the rear and its rear 30mm superstructure wall was mounted at 90°. This provided additional room for both the commander and loader.
Other changes included the layout of the roof, the addition of a commander's cupola with seven periscopes and a 10mm machine gun shield in front of the loader's hatch. The 50mm frontal hull armour was increased to 80mm by addition of 30mm bolted armour plate. Ausf Gs were also mounted with 5mm Schurzen from mid 1943 onwards.
Common field practice was the addition of a layer of concrete added over the armour plate above the driver's position to improve the protection. Models produced between September 1943 and September 1944, were factory applied with Zimmerit (anti-magnetic paste).
Overall, the Sturmgeschutz series proved to be very successful, and served on all fronts as assault guns and tank destroyers in both offensive and defensive mode. Sturmgeschutz III with its low silhouette was a difficult target and a dangerous opponent. Each battery according to organization scheme from November of 1939 had 6 assault guns in three platoons (with 2 assault guns each). In August 1940, Sturmartillerie units were reorganized into Abteilungen (battalions) with 18 assault guns in three batteries (with 6 assault guns each). In early 1941, the battalions were renamed - Sturmgeschuetz Abteilungen and batteries to Sturmgeschuetz Batteries. In March/April of 1941, all Sturmgeschuetz Batteries had the number of assault guns increased to seven. In 1942, with the introduction of long-barrelled Stug III (75mm L/43 and L/48), Sturmgeschuetz Abteilungen were reformed and number of assault guns was increased to 28 per battalion. Each battalion still had three batteries but number of assault guns in platoons was increased to three. In November of 1942, Sturmgeschuetz Abteilungen were reformed again and number of assault guns was increased to 31 per battalion with three additional assault guns for battery commanders. 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 2 Stug III's for each battery command, while each battery had two platoons of four Stug IIIs and one of four StuH 42's. Towards the end of the war, Stugs (40) were often issued to other units as replacement for tank destroyers and even tanks.
In December 1943, the Stug IV was introduced. It was essentially a slightly modified Stug III superstructure mounted on PzKfw IV chassis. It was armed with the 75mm StuK 40 L/48 gun mounted in cast "saukopf" mantlet. It was operated by a 4-man crew. The majority were issued in companies to infantry divisions.

This vehicle entered production in March 1943 and was based on a modified PzKfw IV chassis. The Sturmpanzer IV Brummbär was a close range, direct fire weapon that was developed for street fighting. It was very effective against dug-in infantry positions and buildings. It was also used as a support vehicle for panzer grenadier and infantry units and was first introduced in April 1943.
Early Sturmpanzer IV's suffered from a weight problem, since the recoil and weight of the gun proved to be too much for the chassis and made the vehicle top heavy. In addition, early vehicles were prone to transmission problems and were underpowered, resulting in high fuel consumption. They also lacked a machine gun in the front hull and were easy targets for infantry. A further problem arose from limited storage space in the superstructure. Only 38 150mm rounds were carried, making the operations of the 4 man crew difficult due to the lack of space. The gun could be elevated from -8 to + 30º and traversed by 15º to the left and right.
In October 1943, it was decided to modify the superstructure and the gun to lower the overall weight. In December 1943, a new and lighter version of the gun, designated the 150mm StuH 43/1 L/12, was produced. In December 1943, full production of the second series started.
In mid 1944, the Brummbär superstructure was redesigned and production of this new variant continued until March 1945. Late production models had a ball-mounted MG34 in the front plate of the superstructure. The gun collar and entire layout of the upper part of the superstructure was redesigned reducing the height of the vehicle. Late-production models were also equipped with schürzen and were commonly covered with Zimmerit anti-magnetic paste. In addition, a new commander's cupola with an anti-aircraft gun mount was fitted. The earlier mechanical problems were all but eradicated in the late series vehicles and they proved to be effective weapons. The crew in late models was composed of five men, the commander, who sat behind the gun, two loaders, a gunner and a driver, who sat in a separate compartment on the front left.
Sturmpanzer IV's were formed into Sturmpanzer Battalions. Each Battalion consisted of 45 Sturmpanzer IV's.

Assault guns are reserved for attacks and counterattacks. Their low silhouette permits them to move close behind the leading infantry units, whilst making them difficult to observe and engage. Whenever possible, assault guns are committed in mass at the point of main effort, crossing the start line in conjunction with the infantry.
In the attack, assault guns move in batteries, in extended order, with distances between vehicles varying according to visibility. They rely entirely on the infantry for protection, attempting to stay near the infantry for whom they are furnishing support. Single guns operate under the orders of the nearest infantry commander, but in most cases batteries are kept intact.
Assault guns advance rapidly with the attacking infantry. They are sited in the foremost positions, and seek to engage infantry support weapons, artillery, machine-gun nests, pillboxes, and bunkers, firing from concealed positions whenever possible.
In pursuit, most assault guns move with the advance guard of the advance detachment. Here they will be sited so as to deal with any weak resistance delaying the advance, and to combat tanks.
In the face of moderate resistance, infantry with light machine guns may ride on assault guns. These infantrymen dismount when fired on, and proceed to protect the gun from infantry attack. Assault guns unprotected by infantry are extremely vulnerable.
Assault guns form the backbone of units assigned to seize and defend commanding terrain features. The assault guns are never dug in and remain ready to make the most of their mobility.
When withdrawal becomes necessary, assault guns are assigned to the commander of the rear guard. They normally travel with the rearmost troops, but since they have only one exterior-mounted light machine gun, they continue to rely on infantry protection. In the withdrawal, the task of assault guns is to provide protection for the infantry until they have disengaged.
In attacks on fortified towns and villages, assault guns advance by batteries. Their mission is to destroy the foremost houses. After the infantry has broken into the edge of the town or village, the guns of a battery split up, and by previous arrangement join the various infantry assault groups and fight with them. In village and street fighting, assault guns are considered most useful in breaking up roadblocks, barricades, and fortified houses and work in conjunction with infantry-engineer teams.
In the case of a major breakthrough, assault guns are often withdrawn once open country has been reached and the danger of counterattack has passed. They regroup in mass, while the job of pursuing the enemy and exploiting the breakthrough is taken over by tanks belonging to armored divisions. When tanks encounter difficult infantry-defended terrain or fortified positions, the assault guns are again brought forward into combat.