Even as early as 1939 it was obvious that the days of the little PzKpfw II tank were numbered, for it lacked both armament and armour, However, it was in production and quite reliable, so when the need arose for self-propelled artillery the PzKpfw II was selected to be the carrier for the 10.5- cm (4.13-in) leFH 18 field howitzer. The conversion of the tank hull to carry the howitzer was quite straightforward, for the howitzer was mounted behind an open topped armoured shield towards the rear of the hull and the area where the turret had been was armoured over and the space used for ammunition stowage. Maximum armour thickness was 18 mm (0.7 in).
The result was the self-propelled howitzer known as the Wespe (wasp) though its full official designation was rather more cumbersome: leFH 18/2 auf Fgst Kpfw II (Sf) SdKfz 124 Wespe, but to everyone it was just the Wespe, It was a very popular little self-propelled weapon that soon gained for itself a reputation for reliability and mobility. The first of them were based on the PzKpfw II Ausf F chassis and went into action on the Eastern Front during 1943. On this front they were used by the divisional artillery batteries of the Panzer and Panzergrenadier divisions. They were usually organized into batteries of six howitzers with up to five batteries to an Abteilung (battalion).
The Wespe was so successful in its artillery support role that Hitler himself made an order that all available PzKpfw II chassis production should be allocated to the Wespe alone, and the many other improvised weapons on the PzKpfw II chassis were dropped or their armament diverted to other chassis. The main Wespe construction centre was the Famo plant in Poland, and there production was so rapid that by mid-1944 682 examples had been built. Some time around that date manufacture of the Wespe ceased, but not before 158 had been completed without howitzers; these vehicles had the gap in the armour plate for the howitzer sealed off, the space behind the armour being used for resupply ammunition needed by batteries in the front line.
A typical Wespe went into action carrying its crew of five, including the driver, and 32 rounds of ammunition. A Wespe battery was completely mobile, although some of the vehicles were soft-skinned trucks for carrying ammunition and other supplies. The forward observers were usually carried in light armoured vehicles although some batteries used ex- Czech or captured French tanks for this purpose. Fire orders were relayed back to the battery by radio, and from the battery fire command post the orders were further relayed to the gun positions by land lines, The howitzer carried on the Wespe was the standard 10.5-cm leFH 18 as used by towed batteries (although most were fitted with muzzle brakes) and so used the same ammunition, They also had the same range of 10675m (11,675 yards).
The following comments on the employment of the Wespe were recorded in an experience report written by the commander of the II.Abteitung/Panzer-Artillerie-Regiment 103 on the offensive and defensive battles south of Orel from 5 July to 18 August 1943:
The Abteilung was outfitted with two Batterien each with six le.F.H. auf Panzerfahrgestell ll and one Batterie with six le.F.H. auf Panzerfahrgestell IV. The mixture of calibers (10.5 cm and 15 cm in a 2 to 1 ratio) met all tactical demands. The objective is to combine direct fire from the smaller caliber Panzer’s guns, which score direct hits, with indirect area barrages from artillery, which., because no direct hits are achieved, must gain superiority through its heavier caliber and number of shell fragments.
Since a breakthrough was not achieved, in spite of the massed employment of the Panzer forces (from 8 to 10 July 1943), the Batterien were not employed in mobile offensive actions. Instead, for the most part the Sf.-Abteilung was assigned the same tasks as the other towed Abteilungen in the Artillerie·Regiment, that is supporting attacks with limited objectives against enemy prepared for defense and repulsing enemy attacks.
The advantages of the superior mobility of the Sf.-Artillerie wasn't utilized in supporting swift progressive Panzer and infantry attacks. The actual task for which this Sf.-Artillerie was created did not occur and will not occur in the East until the development of an operational, penetrating Panzer force. However, it is wrong to conclude that Sf.-Artillerie should not exist for the present because:
1. The situation may be different on other fronts, for example, for defending against landing enemy troops by supporting the counterattacks of Panzer units.
2. The advantages of the thoroughly invulnerable Sf.-Artillerie was already decisive during the recent battle of attrition in the East. While the other Abteilungen in the Artillerie-Regiments suffered significant losses in their firing positions because of continuous aerial attacks and counter- battery artillery fire, the Sf.-Abteilung was spared ( because of armor protection and ability to simply drive out of heavy concentrated fire, even though exposed fire positions had to frequently be chosen due to the situation.
3. The armored Sf.-Artillerie were the only batteries that maintained the ability to return fire at exactly the critical moment when the enemy attacked and at the same time the firing positions were covered by counter-battery fire.
4. Even when on the defense, the Sf.-Artillerie made mobile deployment possible and therefore it was possible to continually fire artillery strikes that surprised the enemy. Examples of this is the assembly of the entire Sf.-Abteilung - all 18 howitzers beside each other in at open or concealed map coordinates, carrying out a concentrated sudden artillery strike, directly followed by immediately changing position before effective counter-strikes could occur. However, in practice this last described method of employment couldn't be tested during the almost always critical situations because it was absolutely necessary that all the howitzers in the Abteilung be continuously prepared to fire.
5. The mobile Sf.-Artillerie was capable of defending itself against tanks and infantry that had broken through the defenses. This is of decisive importance during the rapidly shifting battles that occur in the East. Northeastward of SSnamenskoyje, about 50 kilometers northwest of Orel, using direct fire the 4.Batterie effectively engaged eight enemy tanks which attacked the battery’s firing position from the right flank. The howitzers immediately moved to the right and because the tanks were recognized in the open terrain, already opened fire at a range of 1500 meters with a mixture of high explosive and shaped charge shells. As a result of the rapid fire the enemy tanks pulled back and turned off to-ward another direction. Neither side scored a single hit.
6. Because the Sf.-Artillerie is invulnerable to counter-battery fire, it is possible to achieve rapid and heavy concentrated barrages by two or three Batterien pulling into parallel positions in a tight space. As experienced during recent battles, concentrated fire could be rapidly and completely achieved. The only mechanical problems that have shown up on the Wespe are wear on teeth in the steering gear, as well as the brakes being continuously soaked with oil because oil leaks out of the final drive housing. Other mechanical problems haven't occurred with the Wespe in spite of being continuously in action under difficult conditions.