Toward the end of World War II, Germany was in dire need of modern heavy tanks with more powerful guns to fight the new Allied armored vehicles, which mass-produced tank guns could no longer damage with certainty. To strengthen the existing guns without developing new ones, engineers proposed using additional firing chambers. One such project was the Panzerkampfwagen 55 Adler. However, even the experiments underway with multichamber guns and the planned unification with other heavy vehicles failed to save it: the overloaded industry and Germany's defeat conclusively put paid to the prospects of development, which remained at the blueprint phase.