60cm Karl-Gerät "Thor" and 80cm Schwerer Gustav bombarding Sevastopol in 1942

0:00 "Karl-Gerät" (040/041) (German literally "Karl-device"), also known as Mörser Karl, was a World War II German self-propelled siege mortar (Mörser) designed and built by Rheinmetall. Its heaviest munition was a 60 cm (24 in) diameter, 2,170 kg (4,780 lb) shell, and the range for its lightest shell of 1,250 kg (2,760 lb) was just over 10 km (6.2 mi). Each gun had to be accompanied by a crane, a two-piece heavy transport set of railcars, and several modified tanks to carry shells.

Seven guns were built, six of which saw combat between 1941 and 1945. It was used in attacking the Soviet fortresses of Brest-Litovsk and Sevastopol, bombarded Polish resistance fighters in Warsaw, participated in the Battle of the Bulge, and was used to try to destroy the Ludendorff Bridge during the Battle of Remagen. One Karl-Gerät has survived and the remainder were scrapped after the war.

0:37 Schwerer Gustav (English: Heavy Gustav) was a German 80-centimetre (31.5 in) railway gun. It was developed in the late 1930s by Krupp in Rügenwalde as siege artillery for the explicit purpose of destroying the main forts of the French Maginot Line, the strongest fortifications in existence at the time. The fully assembled gun weighed nearly 1,350 tonnes (1,490 short tons), and could fire shells weighing 7 t (7.7 short tons) to a range of 47 km (29 mi).

The gun was designed in preparation for the Battle of France, but was not ready for action when that battle began, and in any case the Wehrmacht's Blitzkrieg offensive through Belgium rapidly outflanked and isolated the Maginot Line's static defences, which were then besieged with more conventional heavy guns until French capitulation. Gustav was later deployed in the Soviet Union during the Battle of Sevastopol, part of Operation Barbarossa, where, among other things, it destroyed a munitions depot located roughly 30 m (98 ft) below ground level. The gun was moved to Leningrad, and may have been intended to be used in the Warsaw Uprising like other German heavy siege pieces, but the uprising was crushed before it could be prepared to fire. Gustav was destroyed by the Germans near the end of the war in 1945 to avoid capture by the Soviet Red Army. Schwerer Gustav was the largest-calibre rifled weapon ever used in combat, and in terms of overall weight, the heaviest mobile artillery piece ever built. It fired the heaviest shells of any artillery piece.