The following piece of history comes to us from The_Warhawk, one of Wargaming's in-house militaria experts.

The Wespe is the colloquial name for the Geschuetzwagen II fuer le.F.H.18/2. It’s actually worth noting that the name ‘Wespe’ was purely a nickname which actually fell out of use by 1944. It was actually ordered by Generaloberst Alfred Jodl to stop using the name, however, the nickname still stuck throughout history. The Wespe is based off of the Pz.Kpfw.II chassis which had been modified to support the weight of its new main armament. The location of the engine and fighting compartment were flipped, with the engine being upfront and the fighting compartment being located towards the after end of the hull. This configuration was originally designed for an earlier self-propelled gun carrying a 7.5cm cannon. As it just happened, the larger 10.5cm could also fit on this chassis, and the end result was the Wespe. The 10.5cm was the preferred divisional artillery piece in use at the time, and had about 40 degrees of total traverse when mounted, and had a range of just over 10 kilometers. Defensive armament was an MG-34 and a pair of MP-38s.

The Wespe was the first self-propelled gun to be produced for German forces, with production beginning early in February 1943. The first units saw action during Operational Citadel (Battle of Kursk). Unlike some of the other vehicles to be implemented for the first time at Kursk (i.e. the Panther ), Wespes actually acquitted themselves reasonably well, at least according to German reports. In particular, they had fairly high survival rates. They were considered well protected against small arms fire, and decently mobile. In at least one instance, they were employed in direct fire against Soviet tanks. Although it’s worth noting that the diminutive vehicle was not as well received in the Mediterranean, where it was considered overweight for the rough Italian landscape.

The Pz.Sfl.IVb actually predates the Wespe, and is a derivative of the Pz.Kpfw.IV , more specifically, it’s based off of the 10.5cm K (gp.Sfl), better known as the ‘ Dicker Max ’. Emphasis should be put on ‘based’. The Pz.Sfl.IVb is a substantially different vehicle, both obviously in role (direct fire vs indirect fire support), but even in terms of configuration. The hull was substantially different. The running gear configuration more closely mirrored that of a Pz.Kpfw. III , with three pairs of road wheels and three return rollers. The driver sat much farther forward which required a different braking system. The transmission was that of the Sfl.IVa. The gun was casemated and had a total of 70 degrees of traverse (that is 35 degrees to both sides), and could operate in direct fire and indirect fire modes. It was planned to even add a fully traversing gun to the vehicle, although these plans never materialized. Infantry protection was provided by a pair of MP.38s, but since it was an artillery piece, and ideally far away from the combat area, that wasn’t a major limiting factor. The first prototype was completed in March 1942, and went into testing with Panzer Division 16, and was considered ready for deployment in 1942. A total of 200 vehicles were ordered, with delivery expected at the start of 1943. This however wasn’t to be. The program was quickly cancelled and efforts were placed onto a different series of self-propelled guns that were not only turreted, but where the guns could be dismounted and converted into a towed configuration.