We bring to you the largest cannons to be ever used in battles. Say hello to the 800mm Schwere Gustav and Dora, railway guns that were developed by Krupp family company. The same company created the Big Bertha cannons in WWI as well. However, these two particular railway guns were used during WWII.
These cannons were designed in 1930s with the primary purpose of taking down the toughest defensive facilities of that time; the Maginot Line in France. It was built by the French along the frontier with Germany. To take them down, the cannons had to be able to annihilate steel that was 1 meter thick or a 7 meter wide wall made of reinforced concrete. However, when war ensued, the Wehrmacht carried out invasion of France via Belgium and thus didnt need to take the Maginot Line down.
Schwerer Gustav weighed in at 1350 tons and could fire 7 ton heavy projectiles from a distance of 47 km. The Gustav super cannons were moved to the Eastern front and took part in the Fall Babarossa. The cannon was used for the siege of Sevastopol for this particular operation, Operation Barbarossa. Afterwards it was moved to Leningrad (St. Petersburg). However, the operation was soon cancelled and the cannon was destroyed to ensure that it didnt end up in hands of the enemy. The other cannon, Dora, was to be used for the siege of Stalingrad, however, the menace of Soviet capturing resulted in German armys withdrawal of Dora from the siege. This cannon was also destroyed before the war ended.
Germans had plans for building a vehicle that can be termed as a fortress capable of propelling itself. The project was named as Landkreuzer P. 1500 Monster and would derive power from 4 submarine diesel engines. It was to be armed with Schwerer Gustav as its main cannon along with two smaller, 150mm howitzers. The project didnt take off and remained on the drawing board until it was cancelled in 1943.