Schwerer Gustav (English: Heavy Gustaf, or Great Gustaf) and Dora were the names of two huge World War II German 80 cm K (E) railway siege guns.
The two guns were developed in the late 1930s by Krupp, the famous German arms manufacturer. Their purpose was to destroy heavy fortifications, especially in the French Maginot Line. The guns weighed nearly 1,350 tonnes, and could fire shells weighing seven tonnes to a range of 37 kilometers (23 mi).
Although they were intended for World War II, they were not ready for action when the Wehrmacht outflanked the Maginot line by sweeping through the low country (Belgium) to start the Battle of France. However, they were ready in Autumn 1941, after the Wehrmacht invaded the Soviet Union (Operation Barbarossa). Gustav was used at the siege of Sevastopol in the summer of 1942. By the end of the siege on 4 July the city of Sevastopol lay in ruins, and 30,000 tons of artillery ammunition had been fired. Gustav had fired 48 rounds and worn out its original barrel, which had already fired around 250 rounds during testing and development. The gun was fitted with the spare barrel and the original was sent back to Krupp's factory in Essen for relining.
Both Gustav and Dora were moved to Leningrad, and may have been intended for Warsaw. Gustav was eventually captured by US troops and cut up, whilst Dora was destroyed near the end of the war to avoid capture by the Red Army.
The Schwerer Gustav was the largest calibre rifled weapon in the history of artillery to see actual combat. It fired the heaviest shells of any artillery piece. A few other huge guns were never fired in anger: the French Monster Mortar (36 French inches; 975mm), the British Mallet's Mortar (36 inch; 914 mm) and the American Little David mortar (36 inch; 910 mm).