laid down; scrapped on slipways. Bismarck – German battleship, scuttled in the Atlantic Ocean after being crippled by Royal Navy torpedo bombers and battleships. Tirpitz – German battleship, sister ship of the aforementioned Bismarck. Sunk in 1944 by RAF Bomber Command; 32 Avro Lancaster bombers dropped blockbuster and Tallboy bombs in Operation Catechism. U-boats Oceangoing U-boats Rocket U-boat – a planned ballistic missile submarine; project abandoned. Type XVIII U-boat – a U-boat designed to use air-independent propulsion; several were under construction when the war ended. Type XXI U-boat "Elektroboot" (Electric boat) – the first U-boat designed to operate completely submerged, 118 were built but only 4 were completed. Type XXIV U-boat – a planned U-boat designed to use air-independent propulsion. Type XXVI U-boat – a U-boat designed to use air-independent propulsion; several were under construction when the war ended. Littoral U-boats Type XXII U-boat – a U-boat designed to use air-independent propulsion; two were under construction. Type XXIII U-boat ("Elektroboot") – a U-boat designed for littoral missions; 67 were built. Type XXV U-boat – a planned all-electric U-boat designed for littoral missions. U-Cruisers Type XI – a U-boat designed to carry the Arado Ar 231 collapsible floatplane and have 128mm turrets; four were laid down but canceled at the outbreak of World War II. Armoured vehicles Anti-aircraft weapons Flakpanzer IV "Kugelblitz" (Ball Lightning) – a Panzer IV-based self-propelled anti-aircraft gun; five prototypes built. Flakpanzer 341 Coelian – A Panther D-based self-propelled anti-aircraft gun, only a wooden mockup of the turret was built. Anti-tank weapons Sturer Emil ("Stubborn Emil") – an experimental Panzerjäger style, open-topped tank destroyer armed with a Rheinmetall 12.8 cm K L/61 gun, 2 prototypes built for tests. Sole surviving prototype on display at the Kubinka Tank Museum. Heavy tanks Tiger I Tiger II Super-heavy tanks Landkreuzer P. 1000 "Ratte" (Rat) – a planned super-heavy tank, weighing 1000 tonnes and armed with two 280mm cannons, one 128mm anti-tank gun, 8 20mm flak guns and 2 15mm heavy machine guns; cancelled in early 1943. Panzer VII "Löwe" (Lion) – a planned super-heavy tank, weighing 90 tonnes and armed with a 105mm cannon; cancelled in March 1942 in favor of the Panzer VIII Maus. Panzer VIII "Maus" (Mouse) – a super-heavy tank, weighing 180 tonnes and armed with two cannons of 128mm and 75mm calibre; five were ordered but only two operable prototypes completed – lone survivor currently on display