Hummel

The Hummel (literally German for Bumblebee) was a SPG developed for the Wehrmacht in light of problems encountered in Operation Barbarossa. It is similar in design to the Sd.Kfz 135, but should not be confused, as the two are entirely seperate vehicles.

IRL

The Hummel was developed as a solution to inadequate performance of existing Self propelled guns on the Eastern Front. Ideas to mount a Howitzer to a Panzer III or Panzer IV chassis with a 105 mm Howitzer were rejected in favor of a new design, which would mount a 149 mm Howitzer.

Enter the Hummel, which entered the war under the technical designation Sd.Kfz 165. They were first deployed alongside their smaller Wespe cousins during the Decisive Battle of Kursk. It was found that the Hummel did not carry enough ammo inside it, and dedicated ammo carrier Hummels were developed with no other mission besides lugging ammo.

In an absolute moment of utter hilarity, Hitler ordered that "Hummel" be dropped from the official technical designation of the vehicle because he thought it sounded dumb. As if King Tiger was any cooler when the things could barely do more than act as stationary turrets