Flak 88mm

Flak 88mm, also known as the eighty-eight, was a German Anti-aircraft gun first employed during the First World War on naval ships. In the Second World War, it earned a rightfully feared reputation among allied pilots, and even allied tank crews when the Germans figured out that they could use it to tell tanks and even bunkers to fuck off.

IRL

The Flak 88 first derives from the 1916 variant, which was developed when battlefield observations determined that traditional Howitzers simply fired too slowly to scare off aircraft, and Machine Guns simply didn't have the range. Therefore, a request was put out for a Heavy AA gun, and they were first fielded with the Kriegsmarine.

Post war, Germany was technically forbidden from having guns of such a caliber, but the Krauts clearly didn't understand what a treaty was, so they requested an 88mm AA gun from Krupp, which they delivered from a collaborative project with the Swedish Bofors company. Early testing and fielding in Spain revealed it was lethally effective in its job, its weapons being more than a match for the relatively pitiful Soviet Polikarpovs being fielded in the theater. Further improvements allowed the gun to be set up in a very small amount of time, which made them even more desirable due to the Blitzkrieg tactics Germany planned to utilize during the war.

In 1941, one variant of these guns was developed into an absolute monster that could throw a shell up to 49,000 feet in the air. They were almost exclusively used in the homeland due to their complexity and their intented targets being Allied bomber crews.

Organizationally, the Flakk 88 was under the jurisdiction of the Luftwaffe, along with all other flak batteries. In spite of Georing's general incompetence, these guns performed excellently in the Anti-tank role when the German army needed them most. . . despite them never actually being designed to be anti-tank guns. The AP shells they did have? They were for bunkers and buildings and that muzzle velocity required to get a shell high enough to deal with bombers meant they were more than a match for the Matilda and the Char-1B in France, and were so loathed in Africa that the Allies worked to develop counters to them. In the Eastern Front, they were invaluable as some of the only weapons that could reliably penetrate Soviet Armor.

The PaK43 is derived from this weapon, which is basically the Flak 88 but as a dedicated AT gun, which was most notoriously used on the King Tiger.