The 12.8 cm PaK (Panzerabwehrkanone) 44 was the largest caliber German anti-tank gun fielded by her armies during World War II. It was designed as a final response to the escalating armor/anti-armor spiral which continued right through the end of the war, and afterward. Experiences with Russian 122-mm guns and the heavy armor of the KV and IS tanks had shown that even the vaunted 88-mm gun had its limitations.
The choice of 128-mm was made due to existing tooling being available for this caliber as naval and anti- aircraft weapons.
Contracts for design and prototypes were awarded to both Krupp and Rheinmetall-Borsig, with testing commencing in late 1944. The Krupp design was chosen for series production, and although performance was impressive, a towed weapon weighing nearly 11-tons was simply not practical. Various carriages, both foreign and domestic were tried, with varying degrees of success.