The Schwerer Gustav and its sister cannon Dora were the two heaviest artillery pieces ever built in terms of overall weight (1350 tonnes) and projectile weight (15,700 pounds), with its 800mm rounds being the heaviest ever fired in battle. The weapons had a range of more than 24 miles. The weapons were initially intended to be used against the French Maginot Line, but the Blitzkrieg rendered that objective obsolete. Instead, the guns were used to fight the Soviet Union on the Eastern Front. During the German siege of Sevastopol in June 1942, the Schwerer Gustav saw action. ¹⁾

The Karl-Gerät was intended to be a siege weapon, specifically to attack the Maginot Line. Its 21-man crew was capable to firing a 600mm heavy bunker-busting shell over 3 miles at a rate of roughly 6 per hour. There were a total of seven of these guns made, one as a test piece and six others that saw substantial battle on both fronts. The Karl-Gerät made its combat debut in June 1941, when a three-gun battery pounded the fortress of Brest-Litovsk during the first phase of Operation Barbarossa. The next year, in June and July of 1942, a battery of Karl-Geräts took part in the siege of Sevastopol. ²⁾