While casemate AFVs played a very important role in World War II (the Sturmgeschütz III for example was the most numerous armored fighting vehicle of the German Army during the entire war), they became much less common in the post-war period. Heavy casemate tank destroyer designs such as the US T28 and the British Tortoise never went beyond prototype status, while casemate vehicles of a more regular weight, such as the Soviet SU-122-54, saw only very limited service. The general decline of casemate vehicles can be seen in the technological progress which resulted in the rise of universal main battle tanks, which unified in them the capability to take up the roles and tasks which in the past had to be diverted between several different classes of vehicles. However, vehicles such as the German Kanonenjagdpanzer of the 1960s still let the casemate concept live on, while the Swedish Army went as far as employing a casemate tank design, the Stridsvagn 103, or "S-Tank", as their main armoured fighting vehicle from the 1960s until the 1990s, favoring it over contemporary turreted designs. Other casemate design ideas, such as the projected German Versuchsträger 1–2 with two main guns, were developed even later.