Duke-class dreadnoughts) were prone to flooding, making the guns ineffective. Shipboard casemate guns were partially rendered obsolete by the arrival of "all-big gun" battleship, pioneered by in 1906, but were reintroduced as the increasing torpedo threat from destroyers forced an increase in secondary armament calibre. Many battleships had their casemates plated over during modernization in the 1930s (or after the Attack on Pearl Harbor, in the case of US vessels) but some, like carried them to the end of World War II. The last ships built with casemates as new construction were the American s of the early 1920s and the 1933 Swedish aircraft cruiser . In both cases the casemates were built into the forward angles of the forward superstructure (and the aft superstructure as well, in the Omahas). Armoured vehicles In regards to armored fighting vehicles, casemate design refers to vehicles that have their main gun mounted directly within the hull and lack the rotating turret commonly associated with tanks. Such a design generally makes the vehicle mechanically simpler in design, less costly in construction, lighter in weight and lower in profile. The saved weight can be used to mount a heavier, more powerful gun or alternatively increase the vehicle's armor protection in comparison to regular, turreted tanks. However, in combat the crew has to rotate the entire vehicle if an enemy target presents itself outside of the vehicle's limited gun traverse arc. This can prove very disadvantageous in combat situations. During World War II, casemate-type armored fighting vehicles were heavily used by both the combined German Wehrmacht forces, and the Soviet Red Army. They were mainly employed as tank destroyers and assault guns. Tank destroyers, intended to operate mostly from defensive ambush operations, did not need a rotating turret as much as offensively used tanks, while assault guns were mainly used against fortified infantry positions and could afford a longer reaction time if a target presented itself outside the vehicle's gun traverse arc. Thus, the weight and complexity of a turret was thought to be unnecessary, and could be saved in favor of more capable guns and armor. In many cases, casemate vehicles would be used as both tank destroyers or assault guns, depending on the tactical situation. The Wehrmacht employed several casemate tank destroyers, initially with the still-Panzerjäger designation Elefant with an added, fully enclosed five-sided (including its armored roof) casemate atop the hull, with later