Wespe

The Wespe Self-propelled gun was an artillery vehicle built from combining chassis of a Panzer II and a 10.5cm leichte Felthaubitze howitzer. It was primarily designed by Alkett and manufactured by the FAMO company.

IRL

Self-propelled artillery as a whole was a rather novel concept in WWII: At the outbreak of the war artillery was still being moved around by tractors or horses. During the battles of Poland and France, the Germans found out that their artillery units often had trouble following the Panzerdivisionen, especially those led by some giggling future Desert Fox that set a record-breaking advance of over 200km in one day on the Dash to the Channel; something horse-drawn guns simply couldn't hope to match. Still, with the Luftwaffe dominating the skies and JU-87 Stuka's that could keep up with the tanks, the situation was not considered too critical by the German High Command at the time.

Fast forward as usual to the invasion of Russia: the war is starting to go south for the Germans, and they start looking (amongst other things) into increasing their artillery's mobility. Waffenprüfamt 6 (the guys responsible for designing tanks and other motorized vehicles) put out a tender for a brand new vehicle that should be fully tracked, armed with at least a 10.5cm artillery gun and with an enclosed and 360° traversable turret. The problem was that this idea was... premature: while indeed such type of vehicles would be developed and fielded to great effect by multiple nations about 20 years after WWII, in 1942 such a vehicle was technologically not yet feasible and none of the big German industrialists answered.

Undaunted, German High Command looked to one of their so-called Zwischenlösungen (lit: in-between solutions) of getting a system that was perhaps not as great as envisioned but would be available immediately with already available resources, in order to give the developer more time to come up with the initial solution. German High Command then turned to an AAR of the unit of a (at the time) Captain Alfred Becker, that after the fall of France had installed his artillery battery on the chassis of obsolete English tankettes to render the big guns more mobile. They then looked at the Marders, where Becker had started with the same general idea of strapping a PaK-40 Anti-Tank Gun to obsolete French chassis, and Alkett had then taken over mounting the PaK's on (just as obsolete) Panzer II chassis. Thus, they went knocking at Alkett's door asking if they could mount a 10.5cm howitzer instead, and the Wespe was born. The design was so popular that Hitler ordered the Panzer II chassis be diverted away from the Marder II program in favor of its production. The initial idea was to produce 1.000 of Wespes over a two-year run then switch to a more advanced model, but as was often the case with the Zwischenlösungen the improved vehicle never saw the light of day and they served throughout the war.

As an interim way to create mobile firepower for the Panzer divisions, the Wespe is in many ways similar to its big brother the Hummel, only it had a "mere" 10.5 cm howitzer. The design was solid, and despite having all the shortcomings of an open topped combat vehicle, the crews who operated the vehicle held them in high regard for their high maneuvrability. Its main limitations were the cramped fighting compartment, the limited ammo and the strain the huge gun put on the chassis and transmission: while the Russian plains didn't give Wespes much trouble, break-downs and consequent abandon of the machine were much more frequent in mountainous Italy.